Multiple host range bacteriophage with hybrid tail fibres

ABSTRACT

Modified bacteriophage, uses thereof, and compositions containing the modified bacteriophage are described. The compositions are useful for human treatment and may treat various conditions, including bacterial infections.

RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 15/517,664 filed Apr. 7, 2017, now U.S. Pat. No. 11,492,601, which is a U.S. National Phase application of International Application No. PCT/EP2015/073294, filed Oct. 8, 2015, which claims priority to United Kingdom Application No. 1417805.7 GB, filed Oct. 8, 2014, each of which is incorporated herein by reference.

The present invention relates to a modified bacteriophage, uses thereof, and compositions containing the modified bacteriophage.

SEQUENCE LISTING

The contents of the electronic sequence listing (1143297.003002.xml; Size: 94,234; and Date of Creation: Sep. 19, 2022) is herein incorporated by reference in its entirety.

BACKGROUND TO THE INVENTION

The World Health Organisation's 2014 report on global surveillance of antimicrobial resistance reveals that antibiotic resistance is a global problem that is jeopardising the ability to treat common infections in the community and hospitals. Without urgent action, the world is heading towards a post-antibiotic era, in which common infections and minor injuries, which have been treatable for decades, can once again kill (WHO, 2014). Antibiotic resistance complicates patients' recovery from even minor operations and is increasingly causing treatment failures. In fact, there are now strains of some genera of bacteria circulating globally which are resistant to all available antibiotics. Such strains commonly fall within the scope of the so-called ESKAPE pathogens—Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter species (Boucher et al., 2009). The term ESKAPE pathogens was coined by Boucher et al., to emphasize that these bacteria currently cause a majority of hospital infections in the US and Europe and can effectively “escape” the majority, if not all, available antibiotics with panantibiotic-resistant infections now occurring. The death rate for patients with serious infections caused by common bacteria treated in hospitals is approximately twice that of patients with infections caused by the same non-resistant bacteria, e.g. people with methicillin-resistant Staphylococcus aureus (MRSA) infections are estimated to be 64% more likely to die than people with a non-resistant form of the infection (WHO, 2014). Of the Gram positive bacteria, methicillin resistant S. aureus continues to be a major cause of morbidity and mortality in hospitals in the US and Europe. However, in more recent years, several highly resistant Gram negative pathogens, including Acinetobacter species, multidrug resistant (MDR) P. aeruginosa, and carbapenem-resistant Klebsiella species and Escherichia coli, have emerged as major pathogens causing serious, and sometimes untreatable, infections. Advances in medicine mean that increasingly complex procedures take place: and these advances are leading to a growing number of elderly patients and patients undergoing surgery, transplantation, and chemotherapy all of which will produce an even greater number of immunocompromised individuals at risk of these infections (Walker et al., 2009). This phenomenon has led to a greater dependence on, and requirement for, effective antibiotics.

P. aeruginosa is one bacterium which is frequently multi-drug resistant (MDR) having intrinsic resistance due to low permeability of its outer membrane limiting drugs getting into the cell, and a multitude of efflux pumps to expel any drugs that successfully manage to enter the cell. P. aeruginosa is also acquiring additional resistance mechanis nce to the “antibiotics of last resort” for Gram negatives, the carbapenems. P. aeruginosa ms, including resista causes approximately 10% of all hospital acquired infections and is the second leading cause of hospital-acquired pneumonia, which accounts for 50% of all hospital-acquired infection prescribing. P. aeruginosa infections in hospitals commonly require intravenous (IV) treatment with current standard of care for P. aeruginosa infections dictating that patients are treated with at least two antibiotics. Unfortunately, resistance frequently develops in patients during therapy. With so few new classes of antibiotic developed and approved for market within the last 30-40 years, there is a critical need for novel, safe and effective antibacterial agents.

As an alternative to conventional antibiotics, one family of proteins which demonstrate broad spectrum antibacterial activity inside bacteria comprises the α/β-type small acid-soluble spore proteins (known henceforth as SASP). Inside bacteria, SASP bind to the bacterial DNA: visualisation of this process, using cryoelectron microscopy, has shown that SspC, the most studied SASP, coats the DNA and forms protruding domains and modifies the DNA structure (Francesconi et al., 1988; Frenkiel-Krispin et al., 2004) from B-like (pitch 3.4 nm) towards A-like (3.18 nm; A-like DNA has a pitch of 2.8 nm). The protruding SspC motifs interact with adjacent DNA-SspC filaments packing the filaments into a tight assembly of nucleo-protein helices. In 2008, Lee et al. reported the crystal structure at 2.1 Å resolution of an α/β-type SASP bound to a 10-bp DNA duplex. In the complex, the α/β-type SASP adopt a helix-turn-helix motif, interact with DNA through minor groove contacts, bind to approximately 6 bp of DNA as a dimer and the DNA is in an A-B type conformation. In this way DNA replication is halted and, where bound, SASP prevent DNA transcription. SASP bind to DNA in a non-sequence specific manner (Nicholson et al., 1990) so that mutations in the bacterial DNA do not affect the binding of SASP. Sequences of α/β-type SASP may be found in appendix 1 of WO02/40678, including SASP-C from Bacillus megaterium which is the preferred α/β-type SASP.

WO02/40678 describes the use as an antimicrobial agent of bacteriophage modified to incorporate a SASP gene. In order to provide effective production of the modified bacteriophage in a bacterial host, WO02/40678 aims to avoid expression of the SASP gene during proliferation of the production host. To this end, the SASP gene was put under the control of an inducible promoter. In one arrangement, the SASP gene was put under the control of a lysis gene promoter which is active only at the end of the bacteriophage life cycle by insertion into the lysis genes of a temperate bacteriophage. In doing so the phage remains viable as a prophage. In another arrangement, the SASP gene could be located elsewhere on the bacteriophage chromosome and placed under the control of a bacteriophage or bacterial promoter whereby the lytic cycle could be left to run its course. In this arrangement, the bacterial promoter would be non-constitutive and could be up-regulated by environmental cues. It was thought that proliferation of the bacterial production host would otherwise be prevented owing to the presence of the SASP gene product, particularly if the SASP gene was under the control of a constitutive promoter.

WO2009019293 describes that effective production of bacteriophage may be achieved where the bacteriophage has been modified to carry a gene encoding a SASP under the control of a promoter which is controlled independently of the bacteriophage, and which is constitutive with no exogenous or in trans regulation necessary or provided. An example is the fbaA promoter from S. aureus which is used to drive expression of the SASP-C gene from Bacillus megaterium and which, when present in multiple copies, for example following infection of target cells, drives toxic levels of SASP expression.

Bacteriophage vectors modified to contain a SASP gene have generally been named SASPject vectors. Once the SASP gene has been delivered to a target bacterium, SASP is produced inside those bacteria where it binds to bacterial DNA and changes the conformation of the DNA from B-like towards A-like. Production of sufficient SASP inside target bacterial cells causes a drop in viability of affected cells.

Bacteriophage have been used as medicines for the treatment of bacterial infections since the 1920s or 30s. Generally, bacteriophage are specific to their bacterial host. Some bacteriophage are temperate and others non-temperate. Temperate phage are able to infect the host cell and integrate into the host cell genome becoming a prophage which is generally harmless to the host cell in this state. Non-temperate or “lytic” phage are only able to replicate in a lytic lifestyle by making new bacteriophage progeny and ending in lysis of the host cell and release of mature phage particles. For useful medicines, the challenge is to provide bacteriophage compositions which can be used to treat infection from a variety of different bacteria in an effective way. It is commonly thought that this is achieved using the most potent bacteriophage compositions available: those with a broadened host range, possibly as a mixture or “cocktail” of bacteriophage, which are obligately lytic and retain viability through replication and release during treatment (Carlton, 1999; Kutateladze and Adamia, 2010). Cocktails of wild type phage have been used to ensure sufficient spectrum of activity against clinical strains of bacteria (Burrowes and Harper, 2012). Such cocktails can consist of up to 20 different and unrelated phage (Abedon 2008). As an alternative to the cocktail approach, E. coli bacteriophage K1-5 has been isolated. This is a naturally-occurring obligately lytic phage which carries more than one host range determinant allowing it to infect and replicate on both K1 and K5 strains of E. coli (Scholl et al, 2001). These phage are considered to be extra potent.

There remains a need to provide improved bacteriophage for use in treating bacterial infections in medicine as well as inhibiting or preventing bacterial cell growth in medical and non-medical situations.

SUMMARY OF THE INVENTION

In a first aspect, the present invention provides a modified bacteriophage capable of infecting a plurality of different target bacteria, which bacteriophage includes an α/β small acid-soluble spore protein (SASP) gene encoding a SASP which is toxic to the target bacteria; wherein the bacteriophage is non-lytic; and wherein the bacteriophage expresses a hybrid host range determinant (HRD) which comprises an amino acid sequence from a plurality of different bacteriophages. The bacterial host specificity of the HRD is advantageously within the same bacterial species.

It has surprisingly been found that a modified bacteriophage may be produced which is capable of infecting a variety of different target bacteria and which is effective for use in medicine even though the bacteriophage is non-lytic. The bacteriophage has an enhanced host range because it expresses a hybrid HRD protein. The hybrid HRD comprises an amino acid sequence from a plurality of different bacteriophages. Bacteriophages according to the invention may be produced by genetic engineering, for example by selecting HRD from closely related phage. Having created such an extra-potent phage, it can then be rendered non-lytic, and hence non-viable and yet still be suitable as a SASPject vector.

The modified bacteriophage may be non-lytic because it comprises an inactivated lysis gene. Insertion of sequence into the lysis gene or removal of the lysis gene would render this gene inactive. The lysis gene may conveniently be inactivated by insertion of the SASP gene.

In one aspect, the term ‘SASP’ as used in the specification refers to a protein with α/β-type SASP activity, that is, the ability to bind to DNA and modify its structure from its B-like form towards A-like form, and not only covers the proteins listed in appendix 1 of WO02/40678, but also any homologues thereof, as well as any other protein also having α/β-type SASP activity. In an alternative aspect, the term ‘SASP’ as used in the specification refers to any protein listed in appendix 1 of WO02/40678, or any homologue having at least 70%, 75%, 80%, 85%, 90%, 92%, 94%, 95%, 96%, 98% or 99% sequence identity with any one of the proteins. listed in appendix 1 of WO02/40678. In another alternative aspect, the term ‘SASP’ as used in the specification refers to any protein listed in appendix 1 of WO02/40678.

The SASP gene may be chosen from any one of the genes encoding the SASP disclosed in Appendix 1 of WO02/40678. In a preferred arrangement the SASP is SASP-C. The SASP-C may be from Bacillus megaterium.

It is preferred that the SASP gene is under the control of a constitutive promoter which is advantageously sufficiently strong to drive production of toxic levels of SASP when the modified bacteria phage is present in multiple copies in the target bacterium. Useful constitutive promoters include pdhA for pyruvate dehydrogenase E1 component alpha sub units, rpsB for the 30S ribosomal protein S2, pgi for glucose-6-phosphate isomerase and the fructose bisphosphate aldolase gene promoter fda. Preferred regulated promoters, active during infection, are lasB for elastase. These promoters are typically from P. aeruginosa. Promoters having a sequence showing at least 90% sequence identity to these promoter sequences may also be used.

The present invention is generally applicable to bacteriophage infecting a variety of different target bacteria. In one arrangement at least one of the target bacteria is Pseudomonas. Advantageously, the plurality of different target of bacteria is a plurality of different Pseudomonas bacteria. An important target is Pseudomonas aeruginosa.

It was not previously considered obvious that use of an obligate lytic phage would be suitable as a SASPject vector, since a requirement of a SASPject vector is that it is specifically not lytic for optimal therapeutic use, giving an increased time window for SASP expression and enabling prevention of rapid lysis upon treatment in vivo, thus limiting the potential release of antibiotic resistance genes and toxic cell wall components which can lead to a dangerous inflammatory response.

The approach described in the present invention is advantageous as compared to the cocktail approach described previously. Mixtures of modified bacteriophage, such as SASPject vectors are identical in structure and genome sequence, other than carrying a different HRD or hybrid HRD. One advantage is that control of the manufacturing process for the mix of SASPjects will be straightforward, which is an important aspect of a pharmaceutical preparation: the process will be materially the same for phage modified to carry a heterologous HRD as they share identical or near-identical biophysical properties. Another advantage is that the in vivo characteristics of the SASPject vectors are likely to be similar, e.g. pharmacokinetics/pharmacodynamics, as each vector is structurally the same or similar.

In the present invention it has been found that phage can be created which are extra-potent obligately-lytic bacteriophage carrying a hybrid HRD. Surprisingly, such phage can be used to make enhanced SASPject vectors by rendering these phage non-lytic and non-viable, by insertion or replacement of a lytic gene(s) with a gene for a SASP. Phage suitable for such modification may be isolated by screening for phage capable of infecting a chosen bacterial species. For instance, phage may be isolated which infect Pseudomonas aeruginosa, by screening for phage from environmental sources which are able to form plaques on representative P. aeruginosa strains (Gill and Hyman, 2010). Isolated phage may have their whole genomes sequenced and annotated. HRD may be tail fibre proteins, which are commonly found to be proteins responsible for the initial recognition/binding to the host bacterium, for instance in phage T4, T5 and T7 (Rakhuba et al., 2010). Alternatively other HRD may be baseplate proteins. Phage genomes may be searched for potential HRD sequences by assessing the homology of all proteins in the phage genome to known sequences, using BLAST searches.

According to the present invention it is preferred that each HRD has a broad host range. This may be defined as the ability to infect >50% of a diverse collection or clinical isolates, totalling at least 35, preferably at least 40, more preferably at least 44, and most preferably >50 in number. Such isolates should be from a range of geographical locations, including Europe, the Americas, and Asia, should carry a diverse range of antibiotic resistance phenotypes, including multi-drug resistant (MDR) strains, and should be from a diverse range of infection sites, such as strains cultured from blood, lung and skin infections. Such isolates can be obtained from public strain collections such as the American Type Culture Collection (ATCC) and the National Collection of Type Cultures (NCTC). Generally, each tail fibre protein comprises a C-terminal receptor binding region for binding to the target bacteria and an N-terminal region linking the C-terminal receptor binding region to the body of the bacteriophage. Each of the C-terminal and N-terminal regions may be from different bacteriophage. In one arrangement, the N-terminal region comprises amino acids 1 to 628 of the tail fibre protein and the C-terminal region comprises the amino acids 629 to 964 of the tail fibre protein.

The C-terminal region may have no more than 96% amino acid sequence identity with the C-terminal region of bacteriophage Phi33 and may be from any one of the bacteriophage Phi33, LBL3, SPM-1, F8, PB1, KPP12, LMA2, SN, 14-1, JG024, NH-4, PTP47, C36, PTP92 and PTP93. Lower amino acid sequence identities in the C-terminal region are preferred. Advantageously the sequence identity is less than 90%, more advantageously less than 80%, preferably less than 70%, more preferably less than 60%, still more preferably less than 50%, particularly preferably less than 40%, more particularly preferably less than 30%. The N-terminal region may have at least 90% and advantageously at least 95% amino acid sequence identity with the N-terminal region of bacteriophage Phi33 and may be from any one of bacteriophage Phi33, LBL3, SPM-1, F8, PB1, KPP12, LMA2, SN, 14-1, JG024, NH-4, PTP47, C36, PTP92 and PTP93. The N-terminal region and the C-terminal region may be from different bacteriophage tail fibre proteins to provide a heterologous tail fibre protein.

It is advantageous to identify phage tail fibre proteins which share sequence identity of greater than 90% in the N-terminal region. For example several phage—Phi33, PTP47, PTP92 and C36—with a broad host range for P. aeruginosa strains (all of these phage infect >60%, when analysed against 260 strains), have been isolated/identified and their genomes sequenced. Analysis of the genome sequences of Phi33, PTP47, PTP92 and C36 reveals that they contain genes encoding putative tail fibre proteins with a high level of sequence identity in the N-terminal region (>95% amino acid sequence identity), following a 2 sequence BLAST alignment, compared to the Phi33 tail fibre amino acids 1-628 (amino acid identity in parentheses): C36 (96%), PTP47 (98%), PTP92 (97%). BLAST searches have shown that these 4 phages are related to 10 other deposited phage genome sequences which, together, form the family of PB1-like phage: PB1, SPM1, F8, LBL3, KPP12, LMA2, SN, JG024, NH-4, 14-1 (Ceyssens et al., 2009). The homology of these putative tail fibre proteins was assessed. Following a 2 sequence BLAST alignment, compared to the Phi33 tail fibre protein (amino acid identity in parentheses): LBL3 (96%), SPM-1 (95%), F8 (95%), PB1 (95%), KPP12 (94%), LMA2 (94%), SN (87%), 14-1 (86%), JG024 (83%), NH-4 (83%), C36 (96%), PTP47 (86%), PTP92 (83%). An alignment of all 14 of the aforementioned phage is shown in FIGS. 13A-13B.

Analysis of the annotated tail fibre protein sequences from these 14 phages reveals that the N-terminal region of the proteins—equivalent to Phi33 tail fibre amino acids 1-628—show an even higher level of sequence identity at the amino acid level than the sequence identity of these proteins over their entire length, in the range of 96-100% for all 14 proteins. Following a 2 sequence BLAST alignment, compared to the N-terminal amino acids 1-628 of the Phi33 tail fibre protein (amino acid identity in parentheses): LBL3 (96%), SPM-1 (96%), F8 (96%), PB1 (96%), KPP12 (98%), LMA2 (99%), SN (99%), 14-1 (97%), JG024 (97%), NH-4 (97%), PTP47 (98%), C36 (96%), PTP92 (97%). However, the C-terminal region of the protein—equivalent to Phi33 tail fibre amino acids 629-964—is not as conserved as the N-terminal region in some of the proteins, the range of sequence identity being typically 57-96%. Following a 2 sequence BLAST alignment, compared to the C-terminal 629-964 amino acids of the Phi33 tail fibre protein (amino acid identity in parentheses): LBL3 (94%), SPM-1 (93%), F8 (93%), PB1 (94%), KPP12 (87%), LMA2 (85%), SN (65%), 14-1 (65%), JG024 (57%), NH-4 (57%), PTP47 (64%), C36 (96%), PTP92 (57%). Analysis of phage tail fibres from other, well characterised, phage has shown that they possess an N-terminal tail base plate binding region and a C-terminal receptor binding region (Veesler and Cambillau, 2011). In experimental analysis of their bacterial strain host range, using plaque assay or growth inhibition tests, the phage Phi33, PTP47, PTP92 and C36 have overlapping but non-identical host range (Table 1). Taken together with the established evidence for the role of the C-terminal region of phage tail fibres being involved in bacterial host receptor binding, and the sequence variation in the C-terminal region of these 4 phage, and their similar but non-identical host range, it is postulated that the C-terminal variation is associated with host range in the phage assessed.

It is further provided, according to this invention, that the genes for a homologous tail fibre protein can be taken from one phage and added to another, replacing the resident tail fibre, based upon their high level of sequence identity in the N-terminal region. The N-terminal region is thought to be involved in the binding of the tail fibre to the phage tail (Veesler and Cambillau, 2011), allowing the formation of viable phage with the host range associated with donor phage's tail fibre. Hybrid tail fibre genes may be made, carrying the conserved N-terminal tail attachment region of the tail fibre from a recipient phage, together with the variable C-terminal receptor-binding region from a homologous donor phage tail fibre protein, using tail fibres genes such as those described herein. Such tail fibre hybrid genes could be used to replace the tail fibres of the phage. This provides an N-terminal region of the hybrid tail fibre (from the recipient phage) and allows the formation of viable phage with the host range associated with donor phage's tail fibre C-terminal receptor-binding region. Transplantation of engineered tail fibre hybrid genes into a recipient phage has been demonstrated in the present invention. Using standard molecular genetic techniques, Phi33 has been modified to carry heterologous tail fibre hybrids from the following phage: PTP92, PTP47, LBL3, SPM-1, F8, PB1, KPP12, LMA2, SN, 14-1, NH-4. All modified phage have been shown to be viable and able to plaque on P. aeruginosa. (The nomenclature of tail fibre hybrids is as follows: As an example, a hybrid gene such that the N-terminal tail attachment region of Phi33 is hybridised with the C-terminal receptor binding region of PTP47 is Phi33(N)PTP47(C).)

In one such modified phage, Phi33 was engineered such that its tail fibre gene carries the C-terminal receptor binding region of PTP92, creating PTP93 (Phi33(N)PTP92(C)).

This was assessed in more detail, by testing the host range against 35 diverse P. aeruginosa clinical isolates. Comparing host range of the progenitor phage (Phi33), the tail fibre donor (PTP92) and the hybrid phage (PTP93), the host range of the PTP93 hybrid phage is equivalent to that of the tail fibre donor phage (PTP92) rather than Phi33, but it was surprisingly found that in some instances PTP93 possesses the host range of Phi33 on strains that PTP92 cannot infect, thus PTP93 inherits the host range of both phages (Table 2). PTP93 possesses a broader host range (92%) than either Phi33 (74%) or PTP92 (66%) (Table 2). PTP93 is an example of an obligately lytic bacteriophage which can be considered as “extra-potent” as it possesses a characteristic above and beyond those exhibited in their unmodified state. Such extra potent phage are suitable for further modification to make SASPject vectors.

Phi33, through assessment of sequence homology by one skilled in the art, can be placed in the group of PB1-like phage (Ceyssens et al., 2009), and may be considered a broad host range phage by the definition given earlier. Such a phage could be isolated by the methods described earlier. Phi33 is suitable for genetic modification to introduce a gene for SASP under the control of a promoter. Such a modified phage would be suitable for use in treating infections caused by susceptible P. aeruginosa bacteria, either on its own or in combination with other modified bacteriophage.

A preferred approach according to the present invention is to use one or more obligately lytic phage, each engineered to carry a SASP gene expressed from a constitutive promoter, each phage being genetically identical other than their tail fibre or tail fibre hybrid gene, and whereby a lytic gene(s) is inactivated. Such phage may be propagated in strains carrying the deleted lytic gene in trans. Preferred obligately lytic phage for modification and for provision of tail fibre genes to create tail fibre genes or tail fibre hybrid genes are phages carrying tail fibre genes which encode predicted proteins that possess >90% amino acid sequence identity in their N-terminal regions compared to N-terminal regions of the tail fibre of other isolated or identified phage. Preferred obligate lytic phage meeting this criterion are Phi33, PTP92, PTP47, LBL3, SPM-1, F8, PB1, KPP12, LMA2, SN, 14-1, NH-4, PTP93, JG024, PTP47 and C36. Such phage can be identified by a simple PCR assay, by subjecting plaques of isolated phage to PCR with primers specific to highly conserved regions in the N-terminal region of the tail genes.

In such a way, suitable phage can be identified without whole genome sequencing. Phage PB1 can be obtained from a public strain collection. Phages need not be isolated or provided in order to generate tail fibre sequences as such sequences may be identified in DNA sequence databases, or other sources of DNA sequences, which may provide the information necessary in order to synthesise and clone, by standard methods, such sequences, or to create hybrid tail fibre sequences.

Particularly preferred phage for modification are PTP93, Phi33, PTP92, PTP47 and C36. Particularly preferred extra-potent obligate lytic phage are: Phi33, modified to carry the tail fibre hybrid Phi33(N)PTP92(C) in place of the resident tail fibre; Phi33 modified to carry the tail fibre hybrid Phi33(N)PTP47(C) in place of the resident tail fibre. In one aspect of the present invention, preferred extra-potent non-lytic SASPject derivatives of Phi33 include: Phi33, modified to carry the tail fibre hybrid Phi33(N)PTP92(C) in place of the resident tail fibre and carrying SASP-C from Bacillus megaterium under the control of the P. aeruginosa ribosomal subunit protein S2 (rpsB) gene promoter in place of the endolysin gene; Phi33 modified to carry the tail fibre hybrid Phi33(N)PTP47(C) in place of the resident tail fibre and carrying SASP-C from Bacillus megaterium under the control of the P. aeruginosa ribosomal subunit protein S2 (rpsB) gene promoter in place of the endolysin gene; Phi33 modified to carry SASP-C from Bacillus megaterium under the control of the P. aeruginosa ribosomal subunit protein S2 (rpsB) gene promoter in place of the endolysin gene. In one preferred aspect, the present invention provides a preferred mixture of SASPject comprising or consisting of the 3 aforementioned SASPjects formulated together.

In a particularly preferred aspect of the present invention, extra-potent non-lytic SASPject derivatives of Phi33 include: Phi33, modified to carry the tail fibre hybrid Phi33(N)PTP92(C) in place of the resident tail fibre and carrying SASP-C from Bacillus megaterium, codon-optimised for expression in P. aeruginosa, under the control of the P. aeruginosa fructose bisphosphate aldolase (fda) gene promoter in place of the endolysin gene; Phi33 modified to carry the tail fibre hybrid Phi33(N)PTP47(C) in place of the resident tail fibre and carrying SASP-C from Bacillus megaterium, codon-optimised for expression in P. aeruginosa, under the control of the P. aeruginosa fructose bisphosphate aldolase (fda) gene promoter in place of the endolysin gene;

Phi33 modified to carry SASP-C from Bacillus megaterium, codon-optimised for expression in P. aeruginosa, under the control of the P. aeruginosa fructose bisphosphate aldolase (fda) gene promoter in place of the endolysin gene. In a particularly preferred aspect the present invention provides a mixture of SASPject comprising or consisting of the 3 aforementioned SASPjects formulated together.

The efficacy of Phi33 carrying the 33(N)92(C) tail fibre, modified to carry an rpsB-SASP-C cassette (PTP110), together with Phi33 modified to carry an rpsB-SASP-C cassette (PTP114) as a mixture, compared to the 2 unmodifed bacteriophage, is shown in FIG. 14 . The mixture of PTP110 and PTP114 achieved a >3 log reduction in viable cells within 3 hours and is more efficacious than Phi33 (˜1.5 log reduction) and PTP92 (no reduction).

A mixture of three modified bacteriophage, designated PT3.8, was constructed and its efficacy in killing P. aeruginosa tested. The mixture consists of: Phi33 carrying the Phi33(N)PTP92(C) tail fibre, modified to carry the fda-SASP-C (P. aeruginosa codon optimised sequence) in place of the endolysin lysis gene (PTP384); Phi33 carrying the Phi33(N)PTP47(C) tail fibre, modified to carry the fda-SASP-C (P. aeruginosa codon optimised sequence) in place of the endolysin lysis gene (PTP385); Phi33 carrying the Phi33(N)Phi33(C) tail fibre, modified to carry the fda-SASP-C (P. aeruginosa codon optimised sequence) in place of the endolysin lysis gene (PTP284).

The efficacy of PT3.8 was tested in a 24 hour time-kill curve experiment against a multi-drug resistant (MDR) clinical isolate (trachea isolation site, antibiotic resistance to ceftazidime, piperacillin-tazobactam and imipenem) of P. aeruginosa, strain 3503 and reference strain ATCC 27853. Briefly, cultures were set up in Luria Bertani (LB) broth supplemented with 5 mM calcium chloride, 5 mM magnesium sulphate and 0.1% glucose (LC broth), and grown at 37° C. 5×10⁵ colony forming units per millilitre (cfu/ml) of P. aeruginosa was incubated with 3×10⁹ plaque forming units per ml (pfu/ml) of PT3.8, or extra LC broth as a control (untreated culture). Samples were removed at 0, 1, 2, 4, 6 and 24 hours for serial dilution and plating on LC agar plates and then overnight incubation at 32° C. For both strains, the viable cell count was reduced from 5×10⁵ cfu/ml to below the limit of detection (102 cfu/ml) within 1 hour of treatment, and no viable cells were detected after 24 hours (FIGS. 15A-15B). In contrast, the untreated control culture grew to between 5×10⁸ and 1×10⁹ cfu/ml for both strains. This demonstrates the ability of PT3.8 to kill clinical strains of P. aeruginosa.

In another time-kill curve experiment, performed as above but over 1 hour, 5×10⁵ cfu/ml of strain 3503 was incubated with 3×10⁹ pfu/ml of PT3.8, or extra LC broth as a control (untreated culture). No viable cells could be detected (limit of detection=1×10² cfu/ml) from 2 minutes onwards, whilst the untreated control culture was at 1×10⁶ cfu/ml by 1 hour, thus demonstrating rapid activity of PT3.8 compared to marketed antibiotics (FIG. 16 ).

PT3.8 was tested in a murine lung infection model. Briefly, animals were anaesthetised and then administered an inoculum of 7.5 log₁₀ cfu of P. aeruginosa strain ATCC 27853 by nasal inhalation. At 2 hours post infection, the mice were treated either with PT3.8 (3×10¹⁰ pfu) or a vehicle (buffer) control by intravenous injection. At 2 and 22 hours post treatment, mice were euthanised by carbon dioxide asphyxiation, and the thoracic cavities opened and the lungs removed and weighed. Lung tissue was homogenised in tryptone soya broth (TSB) and the number of viable cells in the lung tissue was enumerated by serial dilution and plating on Cetrimide agar plates. A control (not treated) group of mice was euthanised at 2 hours post infection and the viable cells in the lung tissue enumerated, to assess the viable cell count in the lung tissue at the time of treatment. There was a rapid reduction in cfu/gram (cfu/g) of lung tissue in the PT3.8 treated mice, reducing by 5-logs at 2 hours post treatment compared to viable cell levels at the time at which the mice were treated (FIG. 17 ). By 22 hours post treatment, the viable cells in the lung tissue of PT3.8 treated mice remained ˜4 logs lower than the counts at the time of treatment, and 4-5 logs lower than in the lung tissue from vehicle treated mice harvested at the same time. This demonstrates efficacy of PT3.8 in vivo.

In another embodiment, an obligately lytic phage may be modified to create a SASPject by replacing or inactivating the lytic gene(s) with SASP under the control of a constitutive promoter, and the tail fibre gene could be deleted altogether. Such phage must be propagated in a strain in which a tail fibre gene or tail fibre hybrid gene is expressed in trans, and the lytic gene is expressed in trans. In such an instance, the SASPject progeny from such a strain would carry a single tail fibre, derived from the propagation strain, yet would lack in their genomes any tail fibre or tail fibre hybrid gene(s). Several such propagation strains could be constructed and the same tail fibre deleted SASPject expressed in each. In this way several different SASPject derivatives could be made, each carrying a different tail fibre or tail fibre hybrid protein. These SASPjects could be used to formulate a mixture.

In another embodiment, an obligately-lytic phage engineered to carry a SASP gene expressed from a constitutive promoter, in place of or inactivating a lytic gene, may be propagated in a host strain carrying the gene(s) for hybrid tail fibre protein(s) in trans under the control of a suitable promoter, and the lytic gene in trans expressed from a suitable promoter. Suitable promoters for the tail fibre hydrid gene(s) may be a phage promoter, particularly the promoter which drives expression of the tail fibre gene in the engineered, obligately-lytic phage. Other suitable promoters are inducible promoters, such as lac, and trp, together with their cognate regulatory proteins. Suitable promoters for the lytic gene may be a phage promoter, particularly the promoter which usually drives expression of the lytic gene in the engineered obligately-lytic phage. Other suitable promoters are inducible promoters, such as lac, and trp, together with their cognate regulatory proteins. The SASPject progeny obtained from such strains are extra-potent and non-lytic, carrying the tail fibre hybrid(s) expressed from the strain in trans as well as their own. Alternatively, the tail fibre gene from the obligately lytic phage may be deleted altogether, providing that a strain is used for propagation in which tail fibre gene(s) or tail fibre hybrid gene(s) are expressed in trans, and the lytic gene is expressed in trans, allowing for the formation of derivative SASPjects. In such an instance, the SASPject progeny from such a strain would carry multiple tail fibres, yet would lack in their genomes any tail fibre or tail fibre hybrid gene(s).

In a further aspect, the present invention provides a composition for inhibiting or preventing bacterial cell growth, which comprises a modified bacteriophage or mixtures thereof as defined herein and a carrier therefor. The modified bacteriophage may be provided in admixture with at least one other modified bacteriophage which is capable of infecting target bacteria, which includes a SASP gene encoding a SASP which is toxic to the target bacteria and which is non-lytic. The at least one other modified bacteriophage may or may not express a plurality of different HRDs. Such compositions may have a wide range of uses and are therefore to be formulated according to the intended use. The composition may be formulated as a medicament, especially for human treatment and may treat various conditions, including bacterial infections. Among those infections treatable according to the present invention are localised tissue and organ infections, or multi-organ infections, including blood-stream infections, topical infections, oral infections including dental carries, respiratory infections and eye infections. The carrier may be a pharmaceutically-acceptable recipient or diluent. The exact nature and quantities of the components of such compositions may be determined empirically and will depend in part upon the routes of administration of the composition.

Routes of administration to recipients include intravenous, intra-arterial, oral, buccal, sublingual, intranasal, by inhalation, topical (including ophthalmic), intra-muscular, subcutaneous and intra-articular. For convenience of use, dosages according to the invention will depend on the site and type of infection to be treated or prevented. Respiratory infections may be treated by inhalation administration and eye infections may be treated using eye drops. Oral hygiene products containing the modified bacteriophage are also provided; a mouthwash or toothpaste may be used which contains modified bacteriophage according to the invention formulated to eliminate bacteria associated with dental plaque formation.

A modified bacteriophage, or mixture thereof, according to the invention may be used as a bacterial decontaminant, for example in the treatment of surface bacterial contamination as well as land remediation or water treatment. The bacteriophage may be used in the treatment of medical personnel and/or patients as a decontaminating agent, for example in a handwash. Treatment of work surfaces and equipment is also provided, especially that used in hospital procedures or in food preparation. One particular embodiment comprises a composition formulated for topical use for preventing, eliminating or reducing carriage of bacteria and contamination from one individual to another. This is important to limit the transmission of microbial infections, particularly in a hospital environment where bacteria resistant to conventional antibiotics are prevalent. For such a use the modified bacteriophage may be contained in Tris buffered saline or phosphate buffered saline or may be formulated within a gel or cream. For multiple use a preservative may be added. Alternatively the product may be lyophilised and excipients, for example a sugar such as sucrose, may be added.

DETAILED DESCRIPTION OF THE INVENTION

This invention will now be described in more detail, by way of example only, and with reference to the accompanying drawings, in which:

FIGS. 1A-1C is a schematic diagram showing construction of plasmids containing lacZΔM15 and Phi33 endolysin;

FIGS. 2A-2D is a schematic diagram showing construction of plasmids with replaced tail fibre sections;

FIGS. 3A-3D is a schematic diagram showing construction of phage with hybrid tail fibre genes, which may be subsequently modified to have endolysin replaced by SASP-C according to the invention;

FIGS. 4A-4D is a schematic diagram showing construction of phage with further hybrid tail fibre genes, which may be subsequently modified to have endolysin replaced by SASP-C according to the invention;

FIGS. 5A-5B is a schematic diagram showing construction of bacteriophage with hybrid tail fibre genes, in which the lacZα marker has been removed;

FIGS. 6A-6D is a schematic diagram showing construction of plasmids in which the endolysin gene is replaced by SASP-C;

FIGS. 7A-7B is a schematic diagram showing production of further bacteriophage according to the invention;

FIGS. 8A-8D is a schematic diagram showing construction of plasmids in which the endolysin gene is replaced by SASP-C codon optimised for expression in P. aeruginosa;

FIG. 9 shows the sequence of the SASP-C gene from Bacillus megaterium strain KM (ATCC 13632), which has been codon optimised for expression in P. aeruginosa;

FIGS. 10A-10D is a schematic diagram showing production of bacteriophage in which the endolysin gene is replaced by SASP-C which has been codon optimised for expression in P. aeruginosa;

FIGS. 11A-11D is a schematic diagram showing production of further bacteriophage according to the invention;

FIGS. 12A-12B is a schematic diagram showing production of further bacteriophage according to the invention;

FIGS. 13A-13E are is a CLUSTAL 2.1 multiple sequence alignment of the tail fibre genes from Phage SPM-1, F8, PB1, C36, LBL3, Phi33, LMA2, KPP12, JG024, PTP92, NH-4, 14-1, PTP47, SN Sequence divergent C-terminal region shaded in grey, sequence conserved N-terminal region unshaded; and

FIG. 14 shows a bar graph of kill of P. aeruginosa by Phi33, PTP92 and a mixture of PTP110 and PTP114 (labelled “Mix”). Bacteria and phage were incubated together at 37° C. and samples removed at 0 and 3 hours for viable cell counting.

FIGS. 15A-15B. 24 hour time-kill curve showing the in vitro efficacy of PT3.8 against P. aeruginosa strains 3503 (FIG. 15A) and ATCC 27853 (FIG. 15B). Cultures were grown in Luria bertani (LB) broth supplemented with 5 mM calcium chloride, 5 mM magnesium sulphate and 0.1% glucose, at 37° C.

FIG. 16 . 60 minute time-kill curve showing the in vitro efficacy of PT3.8 against P. aeruginosa strain 3503. Cultures were grown in Luria bertani (LB) broth supplemented with 5 mM calcium chloride, 5 mM magnesium sulphate and 0.1% glucose, at 37° C.

FIG. 17 . In vivo efficacy of PT3.8 in a murine lung model of infection. Line labelled “0 hour” shows viable cell numbers in the lung tissue at the time of treatment with either vehicle (tris buffered saline containing 1 mM magnesium sulphate, 10 mM calcium chloride and 10% v/v glycerol) or PT3.8 (2 hours post infection with P. aeruginosa). The viable cell counts in lung tissue at 2 and 22 hours post treatment are shown for each animal in each group (group size=6), the geomean for each data set is represented by a horizontal line. For the 22 hour vehicle group, accurate values could be ascertained for only 3 of 6 animals, the viable cell counts for the other 3 animals were >10{circumflex over ( )}11 cfu/ml.

GENERIC PRODUCT COVERING A SINGLE TAIL FIBRE WITHIN AN INDIVIDUAL PHAGE, OR A MIX OF PHAGES WHERE EACH TYPE OF PHAGE HAS A SINGLE, DIFFERENT TAIL FIBRE

Summary of the genetic modification of a lytic bacteriophage to render it non-lytic, and such that it carries one of a number of possible tail fibre variants, in addition to SASP-C under the control of a promoter that usually controls expression of the 30S ribosomal subunit protein S2 gene (rpsB).

Genes can be removed and added to the phage genome using homologous recombination. There are several ways in which phages carrying foreign genes and promoters can be constructed and the following is an example of such methods.

For the construction of a Phi33 derivative it is shown how, using an E. coli/P. aeruginosa broad host range vector, as an example only, the existing tail fibre, or a section of the tail fibre, in the bacteriophage genome may be replaced by an alternative tail fibre or tail fibre section from a different bacteriophage, via homologous recombination. It is also shown as an example only, how the resulting phage may be rendered non-lytic, and how additional DNA sequences, such as the SASP-C gene from B. megaterium under the control of a P. aeruginosa rpsB promoter, or the SASP-C gene from B. megaterium, codon optimised for expression in P. aeruginosa, under the control of a P. aeruginosa fda promoter may be added to the bacteriophage genome via homologous recombination.

A tail fibre gene, or section of a tail fibre gene, from an alternative phage may be cloned between two regions of Phi33 DNA that flank the native tail fibre, or section thereof, along with a lacZα genetic marker, in a broad host range E. coli/P. aeruginosa vector. This plasmid may be introduced into P. aeruginosa, and the resulting strain infected with Phi33. Following harvesting of progeny phage, double recombinants in which the native Phi33 tail fibre or tail fibre section, has been replaced by the new tail fibre or tail fibre section and lacZα, may be isolated by plaquing on a suitable P. aeruginosa (lacZΔM15⁺) host strain using medium containing a chromogenic substrate that detects the action of β-galactosidase.

In a subsequent step, the lacZα marker may be removed from the bacteriophage genomes by making versions of the previously described tail fibre region recombination plasmids that do not contain the lacZα marker, introducing the new plasmids into suitable P. aeruginosa host strains and infecting with the previously modified bacteriophage derivatives of Phi33 carrying the corresponding alternative tail fibre gene, or section thereof, along with the lacZα marker. Recombinants that retain the new tail fibre or tail fibre section, but from which lacZα has been removed, may be isolated by plaquing on a suitable P. aeruginosa (lacZΔM15⁺) host strain using medium containing a chromogenic substrate that detects the action of β-galactosidase.

In a subsequent step, a similar homologous recombination may be used to replace the endolysin gene of Phi33, or of any of the previously described Phi33 derivatives, or similar bacteriophage or similar derivatives, with the gene for SASP-C, under the control of a P. aeruginosa rpsB promoter, while simultaneously adding an E. coli lacZα reporter gene for the identification of recombinant phage. A region consisting of SASP-C controlled by the rpsB promoter, and the E. coli lacZα allele, may be cloned between two regions of Phi33 that flank the endolysin gene, in a broad host range E. coli/P. aeruginosa vector. This plasmid may be transferred to a suitable P. aeruginosa (endolysin⁺ lacZΔM15⁺) strain, and the resulting strain infected by Phi33 or the previously constructed Phi33 derivative (from which the initial lacZα marker has been removed). Progeny phage may be harvested and double recombinants identified by plaquing on P. aeruginosa (endolysin⁺ lacZΔM15⁺), looking for acquisition of the new lacZα reporter on medium containing a chromogenic substrate that detects the action of β-galactosidase.

In an alternative subsequent step, a similar homologous recombination may be used to replace the endolysin gene of Phi33, or of any of the previously described Phi33 derivatives, or similar bacteriophage or similar derivatives, with the gene for SASP-C that has been codon optimised for expression in P. aeruginosa, under the control of a P. aeruginosa fda promoter, while simultaneously adding an E. coli lacZα reporter gene for the identification of recombinant phage. A region consisting of codon optimised SASP-C controlled by the fda promoter, and the E. coli lacZα allele, may be cloned between two regions of Phi33 that flank the endolysin gene, in a broad host range E. coli/P. aeruginosa vector. This plasmid may be transferred to a suitable P. aeruginosa (endolysin⁺ lacZΔM15⁺) strain, and the resulting strain infected by Phi33 or the previously constructed Phi33 derivative (from which the initial lacZα marker has been removed). Progeny phage may be harvested and double recombinants identified by plaquing on P. aeruginosa (endolysin⁺ lacZΔM15⁺), looking for acquisition of the new lacZα reporter on medium containing a chromogenic substrate that detects the action of β-galactosidase.

Since these bacteriophage to be modified are lytic (rather than temperate), another requirement for these described steps of bacteriophage construction is the construction of a suitable host P. aeruginosa strain that carries either the E. coli lacZΔM15 gene at a suitable location in the bacterial genome, or both the Phi33 endolysin gene and the E. coli lacZΔM15 at a suitable location in the bacterial genome, to complement the lacZα or Δendolysin, lacZα phenotypes of the desired recombinant bacteriophage. As an example, the construction of these P. aeruginosa strains may be achieved via homologous recombination using an E. coli vector that is unable to replicate in P. aeruginosa. The genomic location for insertion of the endolysin and lacZΔM15 transgenes should be chosen such that no essential genes are affected and no unwanted phenotypes are generated through polar effects on the expression of adjacent genes. As an example, one such location may be immediately downstream of the P. aeruginosa strain PAO1 phoA homologue.

The E. coli lacZΔM15 allele may be cloned into an E. coli vector that is unable to replicate in P. aeruginosa, between two regions of P. aeruginosa strain PAO1 genomic DNA that flank the 3′ end of phoA. This plasmid may be introduced into P. aeruginosa and isolates having undergone a single homologous recombination to integrate the whole plasmid into the genome selected according to the acquisition of tetracycline (50 μg/ml) resistance. Isolates (lacZΔM15⁺) which have undergone a second homologous recombination event may then be isolated on medium containing 10% sucrose (utilising the sacB counter-selectable marker present on the plasmid backbone).

The Phi33 endolysin gene and the E. coli lacZΔM15 allele may be cloned into an E. coli vector that is unable to replicate in P. aeruginosa, between two regions of P. aeruginosa strain PAO1 genomic DNA that flank the 3′ end of phoA. This plasmid may be introduced into P. aeruginosa and isolates having undergone a single homologous recombination to integrate the whole plasmid into the genome selected according to the acquisition of tetracycline (50 μg/ml) resistance. Isolates (endolysin⁺, lacZΔM15⁺) which have undergone a second homologous recombination event may then be isolated on medium containing 10% sucrose (utilising the sacB counter-selectable marker present on the plasmid backbone).

In a subsequent step, a similar homologous recombination may be used to remove the lacZα marker from the previously described, (lacZα⁺) Phi33 derivatives that have been modified to replace the endolysin gene with the gene for SASP-C, under the control of a P. aeruginosa rpsB promoter. A region consisting of SASP-C controlled by the rpsB promoter, may be cloned between two regions of Phi33 that flank the endolysin gene, in a broad host range E. coli/P. aeruginosa vector. This plasmid may be transferred to a suitable P. aeruginosa (endolysin⁺ lacZΔM15⁺) strain, and the resulting strain infected by the previously described (lacZα)Phi33 derivatives that have been modified to replace the endolysin gene with the gene for SASP-C, under the control of a P. aeruginosa rpsB promoter. Progeny phage may be harvested and double recombinants identified by plaquing on P. aeruginosa (endolysin⁺ lacZΔM15⁺), looking for loss of the lacZα reporter on medium containing a chromogenic substrate that detects the action of β-galactosidase.

In an alternative subsequent step, a similar homologous recombination may be used to remove the lacZα marker from the previously described, (lacZα)Phi33 derivatives that have been modified to replace the endolysin gene with the gene for SASP-C, codon optimised for expression in P. aeruginosa, under the control of a P. aeruginosa fda promoter. A region consisting of SASP-C, codon optimised for expression in P. aeruginosa, controlled by the fda promoter, may be cloned between two regions of Phi33 that flank the endolysin gene, in a broad host range E. coli/P. aeruginosa vector. This plasmid may be transferred to a suitable P. aeruginosa (endolysin⁺ lacZΔM15⁺) strain, and the resulting strain infected by the previously described (lacZα⁺) Phi33 derivatives that have been modified to replace the endolysin gene with the gene for SASP-C, codon optimised for expression in P. aeruginosa, under the control of a P. aeruginosa fda promoter. Progeny phage may be harvested and double recombinants identified by plaquing on P. aeruginosa (endolysin⁺ lacZΔM15⁺), looking for loss of the lacZα reporter on medium containing a chromogenic substrate that detects the action of β-galactosidase.

Experimental Procedures

PCR reactions to generate DNA for cloning purposes may be carried out using Herculase II Fusion DNA polymerase (Agilent Technologies), depending upon the melting temperatures (T_(m)) of the primers, according to manufacturers instructions. PCR reactions for screening purposes may be carried out using Taq DNA polymerase (NEB), depending upon the T_(m) of the primers, according to manufacturers instructions. Unless otherwise stated, general molecular biology techniques, such as restriction enzyme digestion, agarose gel electrophoresis, T4 DNA ligase-dependent ligations, competent cell preparation and transformation may be based upon methods described in Sambrook et al., (1989). Enzymes may be purchased from New England Biolabs or Thermo Scientific. DNA may be purified from enzyme reactions and prepared from cells using Qiagen DNA purification kits. Plasmids may be transferred from E. coli strains to P. aeruginosa strains by conjugation, mediated by the conjugation helper strain E. coli HB 101 (pRK2013). A chromogenic substrate for β-galactosidase, S-gal, that upon digestion by β-galactosidase forms a black precipitate when chelated with ferric iron, may be purchased from Sigma (S9811).

Primers may be obtained from Sigma Life Science. Where primers include recognition sequences for restriction enzymes, additional 2-6 nucleotides may be added at the 5′ end to ensure digestion of the PCR-amplified DNA.

All clonings, unless otherwise stated, may be achieved by ligating DNAs overnight with T4 DNA ligase and then transforming them into E. coli cloning strains, such as DH5a or TOP10, with isolation on selective medium, as described elsewhere (Sambrook et al., 1989).

An E. coli/P. aeruginosa broad host range vector, such as pSM1080, may be used to transfer genes between E. coli and P. aeruginosa. pSM1080 was previously produced by combining the broad host-range origin of replication from a P. aeruginosa plasmid, oriT from pRK2, the tetAR selectable marker for use in both E. coli and P. aeruginosa, from plasmid pRK415, and the high-copy-number, E. coli origin of replication, oriV, from plasmid pUC19.

An E. coli vector that is unable to replicate in P. aeruginosa, pSM1104, may be used to generate P. aeruginosa mutants by allelic exchange. pSM1104 was previously produced by combining oriT from pRK2, the tetAR selectable marker for use in both E. coli and P. aeruginosa, from plasmid pRK415, the high-copy-number, E. coli origin of replication, oriV, from plasmid pUC19, and the sacB gene from Bacillus subtilis strain 168, under the control of a strong promoter, for use as a counter-selectable marker.

Detection of Phi33-Like Phage (PB1-Like Phage Family) Conserved N-Terminal Tail Fibre Regions by PCR

1. Primers for the detection of Phi33-like phage-like tail fibre genes in experimental phage samples may be designed as follows:

The DNA sequences of the tail fibre genes from all sequenced Phi33-like phage (including Phi33, PB1, NH-4, 14-1, LMA2, KPP12, JG024, F8, SPM-1, LBL3, PTP47, C36, PTP92 and SN) may be aligned using Clustal Omega, which is available on the EBI website, and the approximately 2 kb-long highly conserved region mapping to the gene's 5′ sequence may be thus identified (positions 31680-33557 in the PB1 genome sequence, Acc. EU716414). Sections of 100% identity among the 11 tail fibre gene sequences may be identified by visual inspection. Three pairs of PCR primers targeting selected absolutely conserved regions, and amplifying PCR products no longer than 1 kb may be chosen as follows: pair B4500 and B4501, defining a 194 bp-long region; pair B4502 and B4503, defining a 774 bp-long region; and pair B4504 and B4505, defining a 365 bp-long region.

Primer B4500 consists of sequence of PB1 phage genome (Acc. EU716414) ranging from position 31680 to 31697. Primer B4501 consists of sequence of PB1 phage genome (Acc. EU716414) ranging from position 31851 to 31872. Primer B4502 consists of sequence of PB1 phage genome (Acc. EU716414) ranging from position 31785 to 31804. Primer B4503 consists of sequence of PB1 phage genome (Acc. EU716414) ranging from position 32541 to 32558. Primer B4504 consists of sequence of PB1 phage genome (Acc. EU716414) ranging from position 32868 to 32888. Primer B4505 consists of sequence of PB1 phage genome (Acc. EU716414) ranging from position 33213 to 33232.

B4500 (SEQ ID NO: 1) 5′-GTGATCACACCCGAACTG-3′  B4501 (SEQ ID NO: 2) 5′-CGATGAAGAAGAGTTGGTTTTG-3′  B4502 (SEQ ID NO: 3) 5′-ACGCCGGACTACGAAATCAG-3′  B4503 (SEQ ID NO: 4) 5′-TCCGGAGACGTTGATGGT-3′ B4504 (SEQ ID NO: 5) 5′-CCTTTCATCGATTTCCACTTC-3′  B4505 (SEQ ID NO: 6) 5′-TTCGTGGACGCCCAGTCCCA-3′ 

2. Phi33-like tail fibre genes may be detected in experimental phage samples as follows:

Plaques of isolated phage of environmental origin may be picked from agar plates and added to water and incubated for 30 minutes, making plaque soak outs. The plaque soak outs may be diluted and a portion added to PCR reactions containing one or all of the above primer pairs, and PCR may be performed according to a standard protocol. PCR products may be visualised on a 1.5% agarose gel with ethidium bromide staining, and evaluated for their size. PCR products of the correct size for the primer pair used may be gel-extracted and submitted to an external facility for sequencing. Sequencing results may be compared with the available tail fibre gene sequences in order to confirm the identity of the PCR product.

Construction of Plasmids to Generate Pseudomonas aeruginosa Strains Carrying Either the Escherichia coli lacZΔM15 Gene, or Both the Phi33 Endolysin Gene and the Escherichia coli lacZΔM15 Gene, Immediately Downstream of the phoA Locus of the Bacterial Genome

1. Plasmid pSMX200 (FIG. 1 ), comprising pSM1104 carrying DNA flanking the 3′ end of the P. aeruginosa PAO1 phoA homologue, may be constructed as follows.

A region comprising the terminal approximately 1 kb of the phoA gene from P. aeruginosa may be amplified by PCR using primers B4200 and B4201 (FIG. 1 ). The PCR product may then be cleaned and digested with SpeI and BglII. A second region comprising approximately 1 kb downstream of the phoA gene from P. aeruginosa, including the 3′ end of the PA3297 open reading frame, may be amplified by PCR using primers B4202 and B4203 (FIG. 1 ). This second PCR product may then be cleaned and digested with BglII and XhoI. The two digests may be cleaned again and ligated to pSM1104 that has been digested with SpeI and XhoI, in a 3-way ligation, to yield plasmid pSMX200 (FIG. 1 ).

Primer B4200 consists of a 5′ SpeI restriction site (underlined), followed by sequence located approximately 1 kb upstream of the stop codon of phoA from P. aeruginosa strain PAO1 (FIG. 1 ). Primer B4201 consists of 5′ BglII and Mill restriction sites (underlined), followed by sequence complementary to the end of the phoA gene from P. aeruginosa strain PAO1 (the stop codon is in lower case; FIG. 1 ). Primer B4202 consists of 5′ BglII and NheI restriction sites (underlined), followed by sequence immediately downstream of the stop codon of the phoA gene from P. aeruginosa strain PAO1 (FIG. 1 ). Primer B4203 consists of a 5′ XhoI restriction site (underlined), followed by sequence within the PA3297 open reading frame, approximately 1 kb downstream of the phoA gene from P. aeruginosa strain PAO1 (FIG. 1 ).

Primer B4200 (SEQ ID NO: 7) 5′-GATAACTAGTCCTGGTCCACCGGGGTCAAG-3′ Primer B4201 (SEQ ID NO: 8) 5′-GCTCAGATCTTCCTTAAGtcaGTCGCGCAGGTTCAG-3′ Primer B4202 (SEQ ID NO: 9) 5′-AGGAAGATCTGAGCTAGCTCGGACCAGAACGAAAAAG-3′ Primer B4203 (SEQ ID NO: 10) 5′-GATACTCGAGGCGGATGAACATTGAGGTG-3′

2. Plasmid pSMX201 (FIG. 1 ), comprising pSMX200 carrying the Phi33 endolysin gene under the control of an endolysin promoter, may be constructed as follows.

The endolysin promoter may be amplified by PCR from Phi33 using primers B4204 and B4205 (FIG. 1 ). The endolysin gene itself may be amplified by PCR from Phi33 using primers B4206 and B4207 (FIG. 1 ). The two PCR products may then be joined together by Splicing by Overlap Extension (SOEing) PCR, using the two outer primers, B4204 and B4207. The resulting PCR product may then be digested with Mill and BglII, and ligated to pSMX200 that has also been digested with AflII and BglII, to yield plasmid pSMX201 (FIG. 1 ).

Primer B4204 consists of a 5′ AflII restriction site (underlined), followed by a bi-directional transcriptional terminator (soxR terminator, 60-96 bases of Genbank accession number DQ058714), and sequence of the beginning of the Phi33 endolysin promoter region (underlined, in bold) (FIG. 1 ). Primer B4205 consists of a 5′ region of sequence that is complementary to the region overlapping the start codon of the endolysin gene from Phi33, followed by sequence that is complementary to the end of the endolysin promoter region (underlined, in bold; FIG. 1 ). Primer B4206 is the reverse complement of primer B4205 (see also FIG. 1 ). Primer B4207 consists of a 5′ BglII restriction site (underlined), followed by sequence complementary to the end of the Phi33 endolysin gene (FIG. 1 ).

Primer B4204 (SEQ ID NO: 11) 5′-GATACTTAAGAAAACAAACTAAAGCGCCCTTGTGGCGCTTTAGTTTT ATAC TACTGAGAAAAATCTGGATTC -3′ Primer B4205 (SEQ ID NO: 12) 5′-GATTTTCATCAATACTCCTGGATCC CGTTAATTCGAAGAGTCG -3′ Primer B4206 (SEQ ID NO: 13) 5′- CGACTCTTCGAATTAACG GGATCCAGGAGTATTGATGAAAATC-3′ Primer B4207 (SEQ ID NO: 14) 5′-GATAAGATCTTCAGGAGCCTTGATTGATC-3′

3. Plasmid pSMX202 (FIG. 1 ), comprising pSMX201 carrying lacZΔM15 under the control of a lac promoter, may be constructed as follows.

The lacZΔM15 gene under the control of a lac promoter may be amplified by PCR from Escherichia coli strain DH10B using primers B4208 and B4209 (FIG. 1 ). The resulting PCR product may then be digested with BglII and NheI, and ligated to pSMX201 that has also been digested with BglII and NheI, to yield plasmid pSMX202 (FIG. 1 ).

Primer B4208 consists of a 5′ BglII restriction site (underlined), followed by sequence of the lac promoter (FIG. 1 ). Primer B4209 consists of a 5′ NheI restriction site (underlined), followed by a bi-directional transcriptional terminator and sequence complementary to the 3′ end of lacZΔM15 (underlined, in bold; FIG. 1 ).

Primer B4208 (SEQ ID NO: 15) 5′-GATAAGATCTGAGCGCAACGCAATTAATGTG-3′ Primer B4209 (SEQ ID NO: 16) 5′-GATAGCTAGCAGTCAAAAGCCTCCGGTCGGAGGCTTTTGACT TTAT TTTTGACACCAGACCAAC -3′

4. Plasmid pSMX203 (FIG. 1 ), comprising pSMX200 carrying lacZΔM15 under the control of a lac promoter, may be constructed as follows.

The lacZΔM15 gene under the control of a lac promoter may be amplified by PCR from Escherichia coli strain DH10B using primers B4208 and B4209 (FIG. 1 ). The resulting PCR product may then be digested with BglII and NheI, and ligated to pSMX200 that has also been digested with BglII and NheI, to yield plasmid pSMX203 (FIG. 1 ).

Primer B4208 consists of a 5′ BglII restriction site (underlined), followed by sequence of the lac promoter (FIG. 1 ). Primer B4209 consists of a 5′ NheI restriction site (underlined), followed by a bi-directional transcriptional terminator and sequence complementary to the 3′ end of lacZΔM15 (underlined, in bold; FIG. 1 ).

Primer B4208 (SEQ ID NO: 15) 5′-GATAAGATCTGAGCGCAACGCAATTAATGTG-3′ Primer B4209 (SEQ ID NO: 16) 5′-GATAGCTAGCAGTCAAAAGCCTCCGGTCGGAGGCTTTTGACT TTAT TTTTGACACCAGACCAAC -3′

Genetic Modification of Pseudomonas aeruginosa to Introduce the Phi33 Endolysin Gene and Escherichia coli lacZΔM15 Immediately Downstream of the phoA Locus of the Bacterial Genome

1. Plasmid pSMX202 (FIG. 1 ) may be transferred to P. aeruginosa by conjugation, selecting for primary recombinants by acquisition of resistance to tetracycline (50 μg/ml).

2. Double recombinants may then be selected via sacB-mediated counterselection, by plating onto medium containing 10% sucrose.

3. Isolates growing on 10% sucrose may then be screened by PCR to confirm that the endolysin gene and lacZΔM15 have been introduced downstream of the P. aeruginosa phoA gene.

4. Following verification of an isolate (PAX20), this strain may then be used as a host for further modification of Phi33-related bacteriophage, where complementation of both an endolysin mutation and a lacZα reporter are required.

Genetic Modification of Pseudomonas aeruginosa to Introduce the Escherichia coli lacZΔM15 Gene Immediately Downstream of the phoA Locus of the Bacterial Genome

1. Plasmid pSMX203 (FIG. 1 ) may be transferred to P. aeruginosa by conjugation, selecting for primary recombinants by acquisition of resistance to tetracycline (50 μg/ml).

2. Double recombinants may then be selected via sacB-mediated counterselection, by plating onto medium containing 10% sucrose.

3. Isolates growing on 10% sucrose may then be screened by PCR to confirm that lacZΔM15 has been introduced downstream of the P. aeruginosa phoA gene.

4. Following verification of an isolate (PAX21), this strain may then be used as a host for further modification of bacteriophage, where complementation of a lacZα reporter is required.

Construction of a Plasmid to Replace the 3′ Section of the Phi33 Tail Fibre with that of PTP92, Utilising a lacZα Screening Process

1. pSMX204 (FIG. 2 ), comprising pSM1080 carrying the region immediately downstream of the Phi33 tail fibre gene, may be constructed as follows.

A 1 kb region of Phi33 sequence covering the terminal 20 bases of the Phi33 tail fibre, and the adjacent downstream region, may be amplified by PCR using primers B4222 and B4249 (FIG. 2 ). The resulting PCR product may then be cleaned and digested with NheI, and ligated to pSM1080 that has also been digested with NheI and then treated with alkaline phosphatase prior to ligation, yielding plasmid pSMX204 (FIG. 2 ).

Primer B4222 consists of a 5′ NheI restriction site (underlined), followed by sequence from Phi33, approximately 1 kb downstream of the end of the Phi33 tail fibre gene (FIG. 2 ). B4249 consists of 5′ NheI-KpnI-AvrII restriction sites (underlined), followed by sequence complementary to the 3′ end of the Phi33 tail fibre and sequence immediately downstream of the tail fibre open reading frame (FIG. 2 ).

B4222 (SEQ ID NO: 17) 5′-GATAGCTAGCATGGTTTTCACGACCATG-3′ B4249 (SEQ ID NO: 18) 5′-GATAGCTAGCGAGGTACCGACCTAGGTTTTCCAGCGAGTGACGTAA AATG-3′

2. pSMX205 (FIG. 2 ), comprising pSMX204 carrying lacZα, a 3′ section of the PTP92 tail fibre gene sequence, and a region of Phi33 sequence comprising the 5′ end of the tail fibre gene and sequence located immediately upstream of the Phi33 tail fibre gene, may be constructed as follows.

The lacZα open reading frame may be amplified by PCR from pUC19 using primers B4250 and B4252 (FIG. 2 ). The PTP92 tail fibre 3′ section may be amplified by PCR from PTP92 using primers B4251 and B4254 (FIG. 2 ). The lacZα open reading frame may then be joined to the PTP92 tail fibre gene 3′ section by SOEing PCR using the outer primers, B4250 and B4254. A region comprising sequence of the 5′ end of the Phi33 tail fibre gene, and sequence located immediately upstream of the Phi33 tail fibre gene, may be amplified by PCR using primers B4253 and B4229 (FIG. 2 ). This PCR product may then be joined to the PCR product comprising lacZα and the PTP92 tail fibre gene 3′ section, by SOEing PCR using the outer primers B4250 and B4229. The resulting PCR product may then be cleaned and digested with AvrII and KpnI, and ligated to pSMX204 that has also been digested with AvrII and KpnI, yielding plasmid pSMX205 (FIG. 2 ).

Primer B4250 consists of a 5′ AvrII restriction site, followed by sequence complementary to the 3′ end of the lacZα open reading frame (FIG. 2 ). Primer B4252 consists of a 5′ section of sequence that overlaps the 3′ end of the PTP92 tail fibre gene (underlined), followed by sequence of the 5′ end of the lacZα open reading frame. Primer B4251 is the reverse complement of primer B4252 (FIG. 2 ). Primer B4254 consists of 5′ sequence from within the Phi33 tail fibre gene (underlined), followed by sequence within the 3′ end of the PTP92 tail fibre gene (FIG. 2 ). Primer B4253 is the reverse complement of Primer B4254. Primer B4229 consists of a 5′ KpnI restriction site (underlined), followed by sequence that is complementary to a region approximately 1 kb upstream of the tail fibre gene in Phi33 (FIG. 2 ).

Primer B4250 (SEQ ID NO: 19) 5′-GATACCTAGGTTAGCGCCATTCGCCATTC-3′ Primer B4252 (SEQ ID NO: 20) 5′-CTATTCCAGCGGGTAACGTAAAATGACCATGATTACGGATTC-3′ Primer B4251 (SEQ ID NO: 21) 5′-GAATCCGTAATCATGGTCATTTTACGTTACCCGCTGGAATAG-3′ Primer B4254 (SEQ ID NO: 22) 5′-CAAGCGGGCCGGCTGGTCTCTCGGCAATAACTCCTATGTGATC-3′ Primer B4253 (SEQ ID NO: 23) 5′-GATCACATAGGAGTTATTGCCGAGAGACCAGCCGGCCCGCTTG-3′ Primer B4229 (SEQ ID NO: 24) 5′-GATAGGTACCGCGACCGGTCTGTACTTC-3′

Genetic Modification of Phi33 to Replace the 3′ Section of the Tail Fibre Gene with that of PTP92

1. Plasmid pSMX205 (FIG. 2 ; FIG. 3 ) may be introduced into P. aeruginosa strain PAX21 by conjugation, selecting transconjugants on the basis of tetracycline resistance (50 μg/ml), yielding strain PTA20.

2. Strain PTA20 may be infected with phage Phi33, and the progeny phage harvested.

3. Recombinant phage in which the 3′ end of the Phi33 tail fibre gene has been replaced by that of PTP92, and to which lacZα has been added, may be identified by plaquing the lysate from step (2) on P. aeruginosa strain PAX21, onto medium containing S-gal, looking for black plaques, which are indicative of β-galactosidase activity.

4. PCR may be carried out to check that the tail fibre gene has been replaced, and that lacZα is present.

5. Following identification of a verified isolate (PTPX21; FIG. 3 ), this isolate may be plaque purified twice more on P. aeruginosa strain PAX21, prior to further use.

Construction of a Plasmid to Replace the 3′ Section of the Phi33 Tail Fibre with that of PTP47, Utilising a lacZα Screening Process

1. pSMX206 (FIG. 2 ), comprising pSMX204 carrying lacZα, a 3′ section of the PTP47 tail fibre gene sequence, and a region of Phi33 sequence comprising the 5′ end of the tail fibre gene and sequence located immediately upstream of the Phi33 tail fibre gene, may be constructed as follows.

The lacZα open reading frame may be amplified by PCR from pUC19 using primers B4250 and B4258 (FIG. 2 ). The PTP47 tail fibre 3′ section may be amplified by PCR from PTP47 using primers B4259 and B4260 (FIG. 2 ). The lacZα open reading frame may then be joined to the PTP47 tail fibre gene 3′ section by SOEing PCR using the outer primers, B4250 and B4260. A region comprising sequence of the 5′ end of the Phi33 tail fibre gene, and sequence located immediately upstream of the Phi33 tail fibre gene, may be amplified by PCR using primers B4261 and B4229 (FIG. 2 ). This PCR product may then be joined to the PCR product comprising lacZα and the PTP47 tail fibre gene 3′ section, by SOEing PCR using the outer primers B4250 and B4229. The resulting PCR product may then be cleaned and digested with AvrII and KpnI, and ligated to pSMX204 that has also been digested with AvrII and KpnI, yielding plasmid pSMX206 (FIG. 2 ).

Primer B4250 consists of a 5′ AvrII restriction site, followed by sequence complementary to the 3′ end of the lacZα open reading frame (FIG. 2 ). Primer B4258 consists of a 5′ section of sequence that overlaps the 3′ end of the PTP47 tail fibre gene (underlined), followed by sequence of the 5′ end of the lacZα open reading frame. Primer B4259 is the reverse complement of primer B4258 (FIG. 2 ). Primer B4260 consists of 5′ sequence from within the Phi33 tail fibre gene (underlined), followed by sequence within the 3′ end of the PTP47 tail fibre gene (FIG. 2 ). Primer B4261 is the reverse complement of Primer B4260. Primer B4229 consists of a 5′ KpnI restriction site (underlined), followed by sequence that is complementary to a region approximately 1 kb upstream of the tail fibre gene in Phi33 (FIG. 2 ).

Primer B4250 (SEQ ID NO: 19) 5′-GATACCTAGGTTAGCGCCATTCGCCATTC-3′ Primer B4258 (SEQ ID NO: 25) 5′-CTTTTCCAGCGAGTGACGTAAAATGACCATGATTACGGATTC-3′ Primer B4259 (SEQ ID NO: 26) 5′-GAATCCGTAATCATGGTCATTTTACGTCACTCGCTGGAAAAG-3′ Primer B4260 (SEQ ID NO: 27) 5′-CAAGCGGGCCGGCTGGTCTCTCGGCAATAACTCCTATGTGATC-3′ Primer B4261 (SEQ ID NO: 28) 5′-GATCACATAGGAGTTATTGCCGAGAGACCAGCCGGCCCGCTTG-3′ Primer B4229 (SEQ ID NO: 29) 5′-GATAGGTACCGCGACCGGTCTGTACTTC-3′

Genetic Modification of Phi33 to Replace the 3′ Section of the Tail Fibre Gene with that of PTP47

1. Plasmid pSMX206 (FIG. 2 ; FIG. 4 ) may be introduced into P. aeruginosa strain PAX21 by conjugation, selecting transconjugants on the basis of tetracycline resistance (50 μg/ml), yielding strain PTA21.

2. Strain PTA21 may be infected with phage Phi33, and the progeny phage harvested.

3. Recombinant phage in which the 3′ end of the Phi33 tail fibre gene has been replaced by that of PTP47, and to which lacZα has been added, may be identified by plaquing the lysate from step (2) on P. aeruginosa strain PAX21, onto medium containing S-gal, looking for black plaques, which are indicative of β-galactosidase activity.

4. PCR may be carried out to check that the tail fibre gene has been replaced, and that lacZα is present.

5. Following identification of a verified isolate (PTPX22; FIG. 4 ), this isolate may be plaque purified twice more on P. aeruginosa strain PAX21, prior to further use.

Construction of a Plasmid to Remove the lacZα Marker from PTPX21

1. pSMX207 (FIG. 5 ), comprising pSM1080 carrying a 3′ section of the PTP92 tail fibre gene, and a region of Phi33 sequence located immediately downstream of the Phi33 tail fibre gene, may be constructed as follows.

The region of Phi33 sequence located immediately downstream of the Phi33 tail fibre may be amplified by PCR using primers B4222 and B4255 (FIG. 5 ). The 3′ end of the PTP92 tail fibre gene may be amplified by PCR using primers B4256 and B4257 (FIG. 5 ). These two PCR products may then be joined by SOEing PCR, using the two outer primers B4222 and B4257. The resulting PCR product may then be cleaned, digested with NheI, cleaned again, and ligated to pSM1080 that has also been digested with NheI and then treated with alkaline phosphatase prior to ligation, to yield plasmid pSMX207 (FIG. 5 ).

Primer B4255 consists of a 5′ section of the end of the PTP92 tail fibre gene (underlined), followed by sequence immediately downstream of the Phi33 tail fibre gene (FIG. 5 ). Primer B4256 is the reverse complement of primer B4255 (FIG. 5 ). Primer B4257 consists of a 5′ NheI restriction site (underlined), followed by sequence of the terminal 1 kb of the PTP92 tail fibre gene (FIG. 5 ).

Primer B4255 (SEQ ID NO: 29) 5′-CTATTCCAGCGGGTAACGTAAAATGAAATGGACGCGGATCAG-3′ Primer B4256 (SEQ ID NO: 30) 5′-CTGATCCGCGTCCATTTCATTTTACGTTACCCGCTGGAATAG-3′ Primers B4257 (SEQ ID NO: 31) 5′-GATAGCTAGCGGCAATAACTCCTATGTGATC-3′

Genetic Modification of PTPX21 to Remove the lacZα Marker

1. Plasmid pSMX207 (FIG. 5 ; FIG. 3 ) may be introduced into P. aeruginosa strain PAX21 by conjugation, selecting transconjugants on the basis of tetracycline resistance (50 μg/ml), yielding strain PTA22.

2. Strain PTA22 may be infected with phage PTPX21, and the progeny phage harvested.

3. Recombinant phage in which the lacZα marker has been removed may be identified by plaquing the lysate from step (2) on P. aeruginosa strain PAX21, onto medium containing S-gal, looking for white plaques, which are indicative of loss of β-galactosidase activity.

4. PCR may be carried out to check that the tail fibre gene has been retained, and that lacZα has been removed.

5. Following identification of a verified isolate (PTPX23; FIG. 3 ), this isolate may be plaque purified twice more on P. aeruginosa strain PAX21, prior to further use.

Construction of a Plasmid to Remove the lacZα Marker from PTPX22

1. pSMX208 (FIG. 5 ), comprising pSM1080 carrying a 3′ section of the PTP47 tail fibre gene, and a region of Phi33 sequence located immediately downstream of the Phi33 tail fibre gene, may be constructed as follows.

The region of Phi33 sequence located immediately downstream of the Phi33 tail fibre may be amplified by PCR using primers B4222 and B4262 (FIG. 5 ). The 3′ end of the PTP47 tail fibre gene may be amplified by PCR using primers B4263 and B4264 (FIG. 5 ). These two PCR products may then be joined by SOEing PCR, using the two outer primers B4222 and B4264. The resulting PCR product may then be cleaned, digested with NheI, cleaned again, and ligated to pSM1080 that has also been digested with NheI and then treated with alkaline phosphatase prior to ligation, to yield plasmid pSMX208 (FIG. 5 ).

Primer B4262 consists of a 5′ section of the end of the PTP47 tail fibre gene (underlined), followed by sequence immediately downstream of the Phi33 tail fibre gene (FIG. 5 ). Primer B4263 is the reverse complement of primer B4262 (FIG. 5 ). Primer B4264 consists of a 5′ NheI restriction site (underlined), followed by sequence of the terminal 1 kb of the PTP47 tail fibre gene (FIG. 5 ).

Primer B4262 (SEQ ID NO: 32) 5′-CTTTTCCAGCGAGTGACGTAAAATGAAATGGACGCGGATCAG-3′ Primer B4263 (SEQ ID NO: 33) 5′-CTGATCCGCGTCCATTTCATTTTACGTCACTCGCTGGAAAAG-3′ Primers B4264 (SEQ ID NO: 34) 5′-GATAGCTAGCGGCAATAACTCCTATGTGATC-3′

Genetic Modification of PTPX22 to Remove the lacZα Marker

1. Plasmid pSMX208 (FIG. 5 ; FIG. 4 ) may be introduced into P. aeruginosa strain PAX21 by conjugation, selecting transconjugants on the basis of tetracycline resistance (50 μg/ml), yielding strain PTA23.

2. Strain PTA23 may be infected with phage PTPX22, and the progeny phage harvested.

3. Recombinant phage in which the lacZα marker has been removed may be identified by plaquing the lysate from step (2) on P. aeruginosa strain PAX21, onto medium containing S-gal, looking for white plaques, which are indicative of loss of β-galactosidase activity.

4. PCR may be carried out to check that the tail fibre gene has been retained, and that lacZα has been removed.

5. Following identification of a verified isolate (PTPX24; FIG. 4 ), this isolate may be plaque purified twice more on P. aeruginosa strain PAX21, prior to further use.

Construction of a Plasmid to Replace the Endolysin Gene of Phi33, PTPX23, PTPX24, and Similar Phage, by rpsB-SASP-C and lacZα

1. Plasmid pSMX209 (FIG. 6 ), comprising pSM1080 containing regions of Phi33 flanking the endolysin gene, may be constructed as follows.

The region of Phi33 sequence immediately downstream of the endolysin gene may be amplified by PCR using primers B4265 and B4266 (FIG. 6 ). This PCR product may then be cleaned and digested with NdeI and NheI. The region of Phi33 sequence immediately upstream of the endolysin gene may be amplified by PCR using primers B4267 and B4268 (FIG. 6 ). This second PCR product may then be cleaned and digested with NdeI and NheI. The two PCR product digests may then be cleaned again and ligated to pSM1080 that has been digested with NheI and treated with alkaline phosphatase prior to ligation. Clones carrying one insert of each of the two PCR products may be identified by PCR using primers B4265 and B4268, and NdeI restriction digest analysis of the purified putative clones, to identify plasmid pSMX209 (FIG. 6 ).

Primer B4265 consists of a 5′ NheI restriction site (underlined), followed by Phi33 sequence located approximately 340 bp downstream of the Phi33 endolysin gene (FIG. 6 ). Primer B4266 consists of 5′ NdeI and KpnI restriction sites (underlined), followed by sequence of Phi33 that is located immediately downstream of the endolysin gene (FIG. 6 ). Primer B4267 consists of a 5′ NdeI restriction site (underlined), followed by sequence that is complementary to sequence located immediately upstream of the Phi33 endolysin gene (FIG. 6 ). Primer B4268 consists of a 5′ NheI site (underlined), followed by Phi33 sequence that is located approximately 340 bp upstream of the endolysin gene (FIG. 6 ).

Primer B4265 (SEQ ID NO: 35) 5′-GATAGCTAGCTTGGCCAGAAAGAAGGCG-3′ Primer B4266 (SEQ ID NO: 36) 5′-GATACATATGTCGGTACCTATTCGCCCAAAAGAAAAG-3′ Primer B4267 (SEQ ID NO: 37) 5′-GATACATATGTCAATACTCCTGATTTTTG-3′ Primer B4268 (SEQ ID NO: 38) 5′-GATAGCTAGCAATGAAATGGACGCGGATC-3′

2. Plasmid pSMX210 (FIG. 6 ), comprising pSMX209 containing SASP-C under the control of an rpsB promoter, may be constructed as follows.

The SASP-C gene from Bacillus megaterium strain KM (ATCC 13632) may be amplified by PCR using primers B4269 and B4270 (FIG. 6 ). The resulting PCR product may then be digested with KpnI and NcoI. The rpsB promoter may be amplified by PCR from P. aeruginosa using primers B4271 and B4272 (FIG. 6 ). The resulting PCR product may then be digested with NcoI and NdeI. The two digested PCR products may then be cleaned and ligated to pSMX209 that has been digested with KpnI and NdeI, yielding plasmid pSMX210 (FIG. 6 ).

Primer B4269 comprises a 5′ KpnI restriction site, followed by 5 bases, and then a bi-directional transcriptional terminator, and then sequence complementary to the 3′ end of the SASP-C gene from B. megaterium strain KM (ATCC 13632) (underlined, in bold; FIG. 6 ). Primer B4270 comprises a 5′ NcoI restriction site (underlined), followed by sequence of the 5′ end of the SASP-C gene from B. megaterium strain KM (ATCC 13632) (FIG. 6 ). Primer B4271 comprises a 5′ NcoI restriction site (underlined), followed by sequence complementary to the end of the rpsB promoter from P. aeruginosa PAO1 (FIG. 6 ). Primer B4272 comprises a 5′ NdeI restriction site (underlined), followed by sequence of the beginning of the rpsB promoter from P. aeruginosa PAO1 (FIG. 6 ).

Primer B4269 (SEQ ID NO: 39) 5′-GATAGGTACCGATCTAGTCAAAAGCCTCCGACCGGAGGCTTTTGACT TTAGTACTTGCCGCCTAG -3′ Primer B4270 (SEQ ID NO: 40) 5′- GATACCATGGCAAATTATCAAAACGCATC-3′ Primer B4271 (SEQ ID NO: 41) 5′-GATACCATGGTAGTTCCTCGATAAGTCG-3′ Primer B4272 (SEQ ID NO: 42) 5′-GATACATATGCCTAGGGATCTGACCGACCGATCTACTCC-3′

3. pSMX211 (FIG. 6 ), comprising pSMX210 containing lacZα, may be constructed as follows.

lacZα may be PCR amplified using primers B4273 and B4274 (FIG. 6 ). The resulting PCR product may then be digested with KpnI and ligated to pSMX210 that has also been digested with KpnI and treated with alkaline phosphatase prior to ligation, to yield pSMX211 (FIG. 6 ).

Primer B4273 consists of a 5′ KpnI restriction site (underlined), followed by sequence complementary to the 3′ end of lacZα (FIG. 6 ). Primer B4274 consists of a 5′ KpnI restriction site (underlined), followed by sequence of the lac promoter driving expression of lacZα (FIG. 6 ).

Primer B4273 (SEQ ID NO: 43) 5′-GATAGGTACCTTAGCGCCATTCGCCATTC-3′ Primer B4274 (SEQ ID NO: 44) 5′-GATAGGTACCGCGCAACGCAATTAATGTG-3′

Genetic Modification of Phi33, PTPX23, PTPX24, and Similar Phage, to Replace the Endolysin Gene with rpsB-SASP-C and lacZα

1. Plasmid pSMX211 (FIG. 6 ; FIG. 3 ; FIG. 4 ; FIG. 7 ) may be introduced into P. aeruginosa strain PAX20 by conjugation, selecting transconjugants on the basis of tetracycline resistance (50 μg/ml), yielding strain PTA24.

2. Strain PTA24 may be infected in individual experiments with phage Phi33, or PTPX23, or PTPX24, or other similar phage, and the progeny phage harvested.

3. Recombinant phage, in which the endolysin gene has been replaced by rpsB-SASP-C and lacZα, may be identified by plaquing the lysate from step (2) on P. aeruginosa strain PAX20, onto medium containing S-gal, looking for black plaques, which are indicative of β-galactosidase activity.

4. PCR may be carried out to check that the endolysin gene has been replaced, and that rpsB-SASP-C and lacZα are present.

5. Following identification of verified isolates (for example, PTPX25 (FIG. 7 ), PTPX26 (FIG. 3 ), PTPX27 (FIG. 4 )), the isolates may be plaque purified twice more on P. aeruginosa strain PAX20, prior to further use.

Genetic Modification to Remove the lacZα Marker from PTPX25, PTPX26, PTPX27, and Similar Derivatives of Phi33

1. Plasmid pSMX210 (FIG. 6 ; FIG. 3 ; FIG. 4 ; FIG. 7 ) may be introduced into P. aeruginosa strain PAX20 by conjugation, selecting transconjugants on the basis of tetracycline resistance (50 μg/ml), yielding strain PTA25.

2. Strain PTA25 may be infected in individual experiments with phage PTPX25, or PTPX26, or PTPX27, or other similar phage, and the progeny phage harvested.

3. Recombinant phage, in which lacZα marker has been removed, may be identified by plaquing the lysate from step (2) on P. aeruginosa strain PAX20, onto medium containing S-gal, looking for white plaques, which are indicative of loss of β-galactosidase activity.

4. PCR may be carried out to confirm removal of the lacZα marker, while ensuring that rpsB-SASP-C is still present.

5. Following identification of verified isolates (for example, PTP114 (FIG. 7 ), PTP110 (FIG. 3 ), PTPX28 (FIG. 4 )), the isolates may be plaque purified twice more on P. aeruginosa strain PAX20, prior to further use.

Construction of a Plasmid to Replace the Endolysin Gene of Phi33, PTPX23, PTPX24, and Similar Phage, by Fda-SASP-C(Codon Optimised) and lacZα

1. Plasmid pSMX212 (FIG. 8 ), comprising pSM1080 containing regions of Phi33 flanking the endolysin gene, may be constructed as follows.

The region of Phi33 sequence immediately downstream of the endolysin gene may be amplified by PCR using primers B4265 and B4310 (FIG. 8 ). This PCR product may then be cleaned and digested with NheI and XhoI. The region of Phi33 sequence immediately upstream of the endolysin gene may be amplified by PCR using primers B4311 and B4268 (FIG. 8 ). This second PCR product may then be cleaned and digested with XhoI and NheI. The two PCR product digests may then be cleaned again and ligated to pSM1080 that has been digested with NheI and treated with alkaline phosphatase prior to ligation. Clones carrying one insert of each of the two PCR products may be identified by PCR using primers B4265 and B4268, and XhoI restriction digest analysis of the purified putative clones, to identify plasmid pSMX212 (FIG. 8 ).

Primer B4265 consists of a 5′ NheI restriction site (underlined), followed by Phi33 sequence located approximately 340 bp downstream of the Phi33 endolysin gene (FIG. 8 ). Primer B4310 consists of 5′ AvrII and XhoI restriction sites (underlined), followed by sequence of Phi33 that is located immediately downstream of the endolysin gene (FIG. 8 ). Primer B4311 consists of 5′ XhoI and AvrII restriction sites (underlined), followed by sequence that is complementary to sequence located immediately upstream of the Phi33 endolysin gene (FIG. 8 ). Primer B4268 consists of a 5′ NheI site (underlined), followed by Phi33 sequence that is located approximately 340 bp upstream of the endolysin gene (FIG. 8 ).

Primer B4265 (SEQ ID NO: 35) 5′-GATAGCTAGCTTGGCCAGAAAGAAGGCG-3′ Primer B4310 (SEQ ID NO: 45) 5′-GATACCTAGGTCCTCGAGTATTCGCCCAAAAGAAAAG-3′ Primer B4311 (SEQ ID NO: 46) 5′-GATACTCGAGGACCTAGGTCAATACTCCTGATTTTTG-3′ Primer B4268 (SEQ ID NO: 38) 5′-GATAGCTAGCAATGAAATGGACGCGGATC-3′

2. Plasmid pSMX213 (FIG. 8 ), comprising pSMX212 containing SASP-C codon optimised for expression in P. aeruginosa, under the control of an fda promoter, may be constructed as follows.

The SASP-C gene from Bacillus megaterium strain KM (ATCC 13632) may be codon optimised for expression in P. aeruginosa (FIG. 9 ) and synthesised in vitro. The codon optimised SASP-C gene may then be amplified by PCR using primers B4312 and B4313 (FIG. 8 ). The fda promoter may be amplified by PCR from P. aeruginosa using primers B4314 and B4315 (FIG. 8 ). The resulting two PCR products may then be joined by splicing by overlap extension (SOEing) PCR, using the outer primers B4312 and B4314 (FIG. 8 ). The resulting fda-codon optimised SASP-C-terminator PCR product may then be digested with XhoI and AvrII, cleaned, and ligated to pSMX212 that has been digested with XhoI and AvrII, yielding plasmid pSMX213 (FIG. 8 ).

Primer B4312 comprises a 5′ XhoI restriction site, followed by a bi-directional transcriptional terminator, and then sequence complementary to the 3′ end of the SASP-C gene from B. megaterium strain KM (ATCC 13632) that has been codon optimised for expression in P. aeruginosa (underlined, in bold; FIG. 8 ). Primer B4313 comprises sequence of the 3′ end of the fda promoter from P. aeruginosa PAO1 (in bold) followed by sequence of the 5′ end of the codon optimised SASP-C gene. Primer B4314 comprises sequence complementary to the 5′ end of the codon optimised SASP-C gene followed by sequence complementary to the 3′ end of the fda promoter from P. aeruginosa PAO1 (FIG. 8 ). Primer B4315 comprises a 5′ AvrII restriction site (underlined), followed by sequence of the beginning of the fda promoter from P. aeruginosa PAO1 (FIG. 8 ).

Primer B4312 (SEQ ID NO: 47) 5′-GATACTCGAGAGTCAAAAGCCTCCGACCGGAGGCTTTTGACTTCAG TACTTGCCGCCCAG-3′ Primer B4313 (SEQ ID NO: 48) 5′-GATTGGGAGATACGAGAACCATGGCCAACTACCAGAACGC-3′ Primer B4314 (SEQ ID NO: 49) 5′-GCGTTCTGGTAGTTGGCCATGGTTCTCGTATCTCCCAATC-3′ Primer B4315 (SEQ ID NO: 50) 5′-GATACCTAGGAACGACGAAGGCCTGGTG-3′

3. pSMX214 (FIG. 8 ), comprising pSMX213 containing lacZα, may be constructed as follows.

lacZα may be PCR amplified using primers B4316 and B4317 (FIG. 8 ). The resulting PCR product may then be digested with XhoI and ligated to pSMX213 that has also been digested with XhoI and treated with alkaline phosphatase prior to ligation, to yield pSMX214 (FIG. 8 ).

Primer B4316 consists of a 5′ XhoI restriction site (underlined), followed by sequence complementary to the 3′ end of lacZα (FIG. 8 ). Primer B4317 consists of a 5′ XhoI restriction site (underlined), followed by sequence of the lac promoter driving expression of lacZα (FIG. 8 ).

Primer B4316 (SEQ ID NO: 51) 5′-GATACTCGAGTTAGCGCCATTCGCCATTC-3′ Primer B4317 (SEQ ID NO: 52) 5′-GATACTCGAGGCGCAACGCAATTAATGTG-3′

Genetic Modification of Phi33, PTPX23, PTPX24, and Similar Phage, to Replace the Endolysin Gene with Fda-Codon Optimised SASP-C and lacZα

1. Plasmid pSMX214 (FIG. 8 ; FIG. 10 ; FIG. 11 ; FIG. 12 ) may be introduced into P. aeruginosa strain PAX20 by conjugation, selecting transconjugants on the basis of tetracycline resistance (50 μg/ml), yielding strain PTA26.

2. Strain PTA26 may be infected in individual experiments with phage Phi33, or PTPX23, or PTPX24, or other similar phage, and the progeny phage harvested.

3. Recombinant phage, in which the endolysin gene has been replaced by fda-codon optimised SASP-C and lacZα, may be identified by plaquing the lysate from step (2) on P. aeruginosa strain PAX20, onto medium containing S-gal, looking for black plaques, which are indicative of β-galactosidase activity.

4. PCR may be carried out to check that the endolysin gene has been replaced, and that fda-codon optimised SASP-C and lacZα are present.

5. Following identification of verified isolates (for example, PTPX29 (FIG. 12 ), PTPX30 (FIG. 10 ), PTPX34 (FIG. 11 )), the isolates may be plaque purified twice more on P. aeruginosa strain PAX20, prior to further use.

Genetic Modification to Remove the lacZα Marker from PTPX29, PTPX30, PTPX34, and Similar Derivatives of Phi33

1. Plasmid pSMX213 (FIG. 8 ; FIG. 10 ; FIG. 11 ; FIG. 12 ) may be introduced into P. aeruginosa strain PAX20 by conjugation, selecting transconjugants on the basis of tetracycline resistance (50 μg/ml), yielding strain PTA27.

2. Strain PTA27 may be infected in individual experiments with phage PTPX29, or PTPX30, or PTPX34, or other similar phage, and the progeny phage harvested.

3. Recombinant phage, in which lacZα marker has been removed, may be identified by plaquing the lysate from step (2) on P. aeruginosa strain PAX20, onto medium containing S-gal, looking for white plaques, which are indicative of loss of β-galactosidase activity.

4. PCR may be carried out to confirm removal of the lacZα marker, while ensuring that fda-codon optimised SASP-C is still present.

5. Following identification of verified isolates (for example, PTP284 (FIG. 12 ), PTP384 (FIG. 10 ), PTP385 (FIG. 11 )), the isolates may be plaque purified twice more on P. aeruginosa strain PAX20, prior to further use.

REFERENCES

-   Abedon ST. (2008). Bacteriophage Ecology: Population Growth,     Evolution, an Impact of Bacterial Viruses. Cambridge. Cambridge     University Press. Chapter 1. -   Boucher, H. W., Talbot, G. H., Bradley, J. S., Edwards, J. E.,     Gilbert, D., Rice, L. B., & Bartlett, J. (2009). Bad bugs, no drugs:     no ESKAPE! An update from the Infectious Diseases Society of     America. Clinical Infectious Diseases, 48: 1-12. -   Burrowes, B., & Harper, D. R. (2012). Phage Therapy of Non-wound     Infections. Bacteriophages in health and Disease: Bacteriophages in     Health and Disease, Chapter 14: 203-216. -   Carlton, R. M. (1999). Phage therapy: past history and future     prospects. Archivum Immunologiae et Therapiae Experimenialis-English     Edition 47:267-274. -   Ceyssens P, Miroshnikov K. Mattheus W. Krylov V, Robben J. Noben J.     Vanderschraeghe S, Sykilinda N, Kropinski A M, Volckaert     Mesyanzhinov V, Lavigne R. (2009). Comparative analysis of the     widespread and conserved PB1-like viruses infecting Pseudomonas     aeruginosa. Env. Microbiol., 11:2874-2883. -   Francesconi. S. C., MacAlister, T. J., Setlow, B., & Setlow, P.     (1988). Immunoelectron microscopic localization of small,     acid-soluble spore proteins in sporulating cells of Bacillus     subtilis, J Bacteria, 170: 5963-5967, -   Frenkiel-Krispin, D., Sack, R., Englander, J., Shimoni, E.,     Eisenstein, M., Bullitt, E. & Wolf, S. G. (2004). Structure of the     DNA-SspC complex: implications for DNA packaging, protection, and     repair in bacterial spores. J. Bacteria 186:3525-3530. -   Gill J J, Hyman P. (2010). Phage Choice, Isolation and Preparation     for Phage therapy. Current Pharmaceutical Biotechnology. 11:2-14. -   Kutateladze, M., & Adamia, R. (2010). Bacteriophages as potential     new therapeutics to replace or supplement antibiotics. Trends     Biotechnol. 28:591-595. -   Lee, K. S., Bumbaca, D., Kosman, J., Setlow, P., & Jedrzejas, M. J.     (2008). Structure of a protein-DNA complex essential for DNA     protection in spores of Bacillus species. Proc. Natl. Acad. Sci.     105:2806-2811, -   Nicholson W L, Setlow B, Setlow P. (1990). Binding of DNA in vitro     by a small, acid-soluble spore protein from Bacillus subtilis and     the effect of this binding on DNA topology. J Bacteriol.     172:6900-6906. -   Rakhuba D V, Kolomiets E I, Szwajcer Dey E, Novik E I. (2010).     Bacteriophage Receptors, Mechanisms of Phage Adsorption and     Penetration into Host Cell. Polish J. Microbiol. 59:145-155. -   Sambrook, J., Fritsch, E. F., & Maniatis, 1. (1989). Molecular     cloning (Vol. 2, pp. 14-9). New York: Cold Spring Harbor Laboratory     Press. -   Scholl, D., Rogers, S., Adhya, S., &. Merril, C. R. (2001).     Bacteriophage K1-5 encodes two different tail fiber proteins,     allowing it to infect and replicate on both K1 and 15 strains of     Escherichia coli. J. Virol. 75:2509-2515. -   Veesler D, Cambillau C. (2011). A Common Evolutionary Origin for     Tailed-Bacteriophage Functional Modules and Bacterial Machineries.     Microbiol Mol Biol Rev. 75:423-433. -   Walker, B., Barrett, S., Polasky, S., Galaz, V., Folke, C.,     Engstrom, G., & de Zeeuw, A. (2009). Looming global-scale failures     and missing institutions. Science, 325:1345-1346. -   WHO (2014) Antimicrobial resistance: global report on surveillance     2014.

TABLE 1 Host range of Phi33, PTP92, C36 and PTP47 against 44 European clinical isolates of Pseudomonas aeruginosa. Strains were tested for sensitivity to each phage by dropping 10 μl of crude phage lysate onto a soft agar overlay plate inoculated with bacteria. Plates were grown overnight at 32° C. and the strains were scored for sensitivity to each phage by assessing clearance zones at the point of inoculation. Where phage inhibited growth, as seen by clearance of the bacterial lawn, the strain was marked as sensitive (+), and where no inhibition of growth was seen, the strain was marked as not-sensitive (−) Bacterial Strain no. Phi33 PTP47 PTP92 C36 2019 + + − + 2020 + + − + 2021 + + + + 2029 + + − + 2031 + + + + 2039 + + + + 2040 + + − + 2041 + + + + 2042 + + + + 2045 − − + − 2046 + + + + 2047 + + + + 2048 + + + + 2049 + + + + 2050 + + + + 2051 + + − − 2052 − − − − 2053 + + − + 2054 − + − + 2055 + + − + 2056 + + + + 2057 + + + + 2058 + + + + 2483 − − + − 2484 + + − + 2705 + + − + 2706 + + − + 2707 + + − + 2708 + + + + 2709 + + + + 2710 − + + − 2711 + + + + 2712 + + − + 2713 − + + + 2714 + + + + 2715 + + + + 2716 + + − − 2717 − + + + 2718 − + + + 2719 + + − + 2720 + + + + 2721 + + + + 2722 + + + + 2723 + + − +

TABLE 2 Host range of Phi33, PTP92 and PTP93 against 35 European clinical isolates of Pseudomonas aeruginosa. Strains were tested for sensitivity to each phage by dropping 10 μl of crude phage lysate onto a soft agar overlay plate inoculated with bacteria. Plates were grown overnight at 32° C. and the strains were scored for sensitivity to each phage by assessing clearance zones at the point of inoculation. Where phage inhibited growth, as seen by clearance of the bacterial lawn, the strain was marked as sensitive (+), and where no inhibition of growth was seen, the strain was marked as not-sensitive (−) Isolate Phi33 PTP93 PTP92 2019 + + − 2020 + + − 2029 + + − 2040 + + − 2045 − + + 2053 + + - 2483 − + + 2484 + + − 2705 + − − 2710 − + + 2711 + − + 2712 + + − 2713 − + + 2716 + + − 2717 − + + 2718 − + + 2720 + + + 2721 + + + 2722 + + + 2723 + − − 2728 − + + 2733 + + − 2734 + + + 2740 − + + 2741 + + + 2742 + + + 2743 + + + 2747 + + + 2748 + + + 2749 + + − 2750 + + + 2752 + + + 2753 − + + 2754 + + + 2756 + + + 

1-38. (canceled)
 39. A modified bacteriophage capable of infecting a plurality of different target bacteria, wherein: (a) said bacteriophage includes an α/β small acid-soluble spore protein (SASP) gene encoding a SASP which is toxic to the target bacteria; (b) said bacteriophage expresses a single hybrid host range determinant protein which comprises an amino acid sequence derived from amino acid sequences of range determinant proteins from at least two different bacteriophages, and (c) said hybrid host range determinant protein is a tail fiber protein, (d) wherein said hybrid host range determinant protein comprises an N-terminal region wherein said N-terminal region binds to the body of said bacteriophage and a C-terminal region wherein said C-terminal region comprises a receptor binding region for binding to the target bacteria and wherein the amino acid sequence of said N-terminal region of said hybrid host range determinant protein is derived from a different bacteriophage than the amino acid sequence of said C-terminal region.
 40. A modified bacteriophage according to claim 39 wherein said N-terminal region of said hybrid host range determinant protein comprises amino acids 1 to 628 of said hybrid host range determinant protein based on the amino acid sequence of bacteriophage Phi33 and said C-terminal region comprises amino acids 629 to 964 of the said hybrid host range determinant protein, based on the amino acid sequence of bacteriophage Phi33.
 41. A modified bacteriophage according to claim 39 wherein said N-terminal region is from any one of bacteriophage Phi33, LBL3, SPM-1, F8, PB1, KPP12, LMA2, SN, 14-1, JG024, NH4, PTP47, PTP92, C36 and PTP93 and/or said C-terminal region is from any one of bacteriophage Phi33, LBL3, SPM-1, F8, PB1, KPP12, LMA2, SN, 14-1, JG024, NH4, PTP47, PTP92, C36 and PTP93.
 42. A modified bacteriophage according to claim 39, wherein the percent amino sequence identity of said C-terminal region of said hybrid host range determinant protein to the corresponding C-terminal region of the tail fiber protein of the bacteriophage from which the N-terminal region of said hybrid host range determinant protein is derived is less than 80%, or less than 70%, or less than 60%.
 43. A modified bacteriophage according to claim 39, wherein the C-terminal region has no more than 96% amino acid sequence identity with the C-terminal region of bacteriophage Phi33 and/or the N-terminal region has at least 95% amino acid sequence identity with the N-terminal region of bacteriophage Phi33.
 44. A modified bacteriophage according to claim 39, wherein the bacterial host specificity of the host range determinant is within the same bacterial genus, optionally wherein said bacterial host genus is Pseudomonas.
 45. A modified bacteriophage according to claim 44, wherein said Pseudomonas bacteria comprise Pseudomonas aeruginosa.
 46. A modified bacteriophage according to claim 39, wherein the hybrid host range determinant protein confers a broad host range as defined by more than 50% of a collection of at least 35 or 50 clinical isolates, from a plurality of different infection sites and including a range of antibiotic resistance phenotypes.
 47. A modified bacteriophage according to claim 39 wherein the bacteriophage is non-lytic.
 48. A modified bacteriophage according to claim 47, which comprises an inactivated lysis gene.
 49. A modified bacteriophage according to claim 49, wherein the lysis gene is inactivated by insertion of said SASP gene.
 50. A modified bacteriophage according to claim 39, wherein the SASP is SASP-C.
 51. A modified bacteriophage according to claim 51, wherein the SASP-C is from Bacillus megaterium.
 52. A modified bacteriophage according to claim 39, wherein the SASP gene is under the control of a constitutive promoter which is sufficiently strong to drive production of toxic levels of SASP when the modified bacteriophage is present in multiple copies in the target bacterium and/or wherein the constitutive promoter is selected from pdhA, rpsB, pgi, fda, lasB and promoters having more than 90% sequence identity thereto.
 53. A composition for inhibiting or preventing bacterial cell growth, which comprises at least one modified bacteriophage according to any one of claim 39, and a carrier therefor, wherein said composition is formulated for pharmaceutical use, including topical administration, systemic administration, ocular administration, intravenous administration, and/or respiratory administration or is formulated for environmental use, including bacterial decontamination, surface bacterial contamination, land remediation and/or water treatment.
 54. A composition according to claim 53, comprising: (i) a first modified Phi33 bacteriophage comprising (1) a chimeric tail fiber wherein the N terminal region of the tail fiber is from Phi33 and the C-terminal region of the hybrid tail fiber is from PTP92, (2) a Pseudomonas aeruginosa codon-optimized SASP-C gene operably linked to the fda promoter, and (3) an inactivated lysis gene, wherein the lysis gene is inactivated by insertion of said SASP-C gene therein; and (ii) a second modified Phi33 bacteriophage comprising (1) a chimeric tail fiber wherein the N terminal region of the tail fiber is from Phi33 and the C-terminal region of the hybrid tail fiber is from PTP47, (2) a Pseudomonas aeruginosa codon-optimized SASP-C gene operably linked to the fda promoter, and (3) an inactivated lysis gene, wherein the lysis gene is optionally inactivated by insertion of said SASP-C gene therein.
 55. A composition according to claim 54, further comprising a third modified Phi33 bacteriophage, wherein the modifications consist of the incorporation of a Pseudomonas aeruginosa codon optimized SASP-C gene operably linked to the fda promoter, and (3) an inactivated lysis gene, wherein the lysis gene is inactivated by insertion of said SASP-C gene therein.
 56. A method of treatment of bacterial infection in a subject in need thereof, comprising administration to the subject an effective amount of the composition of claim
 53. 57. A method of treatment of bacterial infection in a subject in need thereof, comprising administration to the subject an effective amount of the composition of claim
 54. 58. A method of treatment of bacterial infection in a subject in need thereof, comprising administration to the subject an effective amount of the composition of claim
 55. 